Antioxidant Activity and Protecting Health Effects of Common Medicinal Plants

CHAPTER THREE

Antioxidant Activity and Protecting Health Effects of Common Medicinal Plants Soňa Škrovánková*,1, Ladislava Mišurcová†, Ludmila Machů* *Department of Food Analysis and Chemistry, Faculty of Technology, Tomas Bata University in Zlı´n, Zlı´n, Czech Republic † Department of Food Technology and Microbiology, Faculty of Technology, Tomas Bata University in Zlı´n, Zlı´n, Czech Republic 1 Corresponding author: e-mail address: [email protected]

Contents 1. Introduction 2. Oxidative Processes and Importance of Antioxidants 2.1 Implication of oxidation processes in foods 2.2 Importance of antioxidants for humans 3. Antioxidants in Medicinal Plants 3.1 Phenolic compounds 3.2 Vitamins 3.3 Further antioxidants in medicinal plants 4. Medicinal Plants as Sources of Antioxidants 4.1 Lamiaceae family 4.2 Apiaceae family 4.3 Zingiberaceae family 4.4 Ginkgoaceae family 4.5 Asteraceae family 4.6 Myrtaceae family 5. Antioxidant Activity of Medicinal Plants 5.1 Determination of antioxidant activity 6. Protecting Health Effects of Medicinal Plants 6.1 Antimicrobial effect 6.2 Anticancer effect 6.3 Influences on cardiovascular diseases 6.4 Additional health effects 7. Conclusion References

Advances in Food and Nutrition Research, Volume 67 ISSN 1043-4526 http://dx.doi.org/10.1016/B978-0-12-394598-3.00003-4

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Abstract Medicinal plants are traditionally used in folk medicine as natural healing remedies with therapeutic effects such as prevention of cardiovascular diseases, inflammation disorders, or reducing the risk of cancer. In addition, pharmacological industry utilizes medicinal plants due to the presence of active chemical substances as agents for drug synthesis. They are valuable also for food and cosmetic industry as additives, due to their preservative effects because of the presence of antioxidants and antimicrobial constituents. To commonly used medicinal plants with antioxidant activity known worldwide belong plants from several families, especially Lamiaceae (rosemary, sage, oregano, marjoram, basil, thyme, mints, balm), Apiaceae (cumin, fennel, caraway), and Zingiberaceae (turmeric, ginger). The antioxidant properties of medicinal plants depend on the plant, its variety, environmental conditions, climatic and seasonal variations, geographical regions of growth, degree of ripeness, growing practices, and many other factors such as postharvest treatment and processing. In addition, composition and concentration of present antioxidants, such as phenolic compounds, are related to antioxidant effect. For appropriate determination of antioxidant capacity, the extraction technique, its conditions, solvent used, and particular assay methodology are important.

1. INTRODUCTION Since the prehistoric time, many medicinal plants were used in folk medicine. They have been used all over the world for thousands of years as natural medicines possessing therapeutic and other pharmacologic effect. Today, according to the World Health Organization (WHO), as many as 80% of the world’s people depend on traditional medicine for their primary health-care needs. The preliminary results of a study on behalf of WHO have shown that the number of individuals using medicinal plants is large and on the increase, even among young people (WHO, IUCN, & WWF, 1993). Medicinal plants or parts of these plants (leaves, rhizomes, roots, seeds, flowers) can be utilized in different forms such as fresh crude form and preparations as teas, decoctions, powdered plant material, or extracted forms of medicinal agents (juices, water or alcohol extracts, tinctures, essential oils, resins, balsams). In the pharmaceutical industry, medicinal plants are valued for their chemical constituents—active substances such as polyphenols and flavonoids, glycosides, alkaloids, and tannins, which may be used as agents in the synthesis of drugs. Besides medical purposes, they could be important in nutrition as they contain many biologically active substances such as vitamins or components of essential oils. They are also used in food industry and cosmetics due to their preservative effect because of the presence of antioxidants and

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antimicrobial constituents and due to the flavoring and dyeing properties of some medicinal plants. Utilization of many medicinal plants for culinary purposes is also very popular in the everyday diet, to flavor various meals and foods. They are widespread in Eastern region and in Western countries too. In recent decades, in the developed world, especially in the United States, a strong desire for things that are natural has appeared. Even if the natural and artificial exemplars are specified to be chemically identical, a majority of people who prefer natural continue to prefer it (Rozin et al., 2004). Therefore, medicinal plants as natural source could be of great economic importance not only because of their utilization in medicine but also as food additives (e.g., as antioxidants due to their strong antioxidant effect) extracted from natural sources. Medicinal plants are generally known and popular for a number of health benefits such as decreasing of blood pressure, prevention of cardiovascular diseases, or reducing the risk of cancer also due to their antioxidant activity. Medicinal plants contain high levels of antioxidants that can delay or inhibit the oxidation of lipids or other molecules. Many lipid-oxidation products are known to interact with biological materials to cause cellular damage, so oxidation process has been associated with chronic diseases such as cancer. General recommendation for the consumers is to increase the consumption of foods containing antioxidants. Thus, the regular sufficient intake of these foods (fruits, vegetables, teas, wine, medicinal plants, and their preparations) could be a good possibility to support the health condition. However, the effective physiological relevance of their intake is meanwhile uncertain as many studies are mainly based on in vitro assays that do not necessarily reflect the human physiological mechanisms in vivo (Becker, Nissen, & Skibsted, 2004). Therefore, the effects of dietary antioxidants in vivo should be studied intensively to know their physiological effects. This chapter is focused on the characterization of oxidative processes and antioxidants, profile of medicinal plant antioxidants, their benefits, and protecting health effects of common medicinal plants.

2. OXIDATIVE PROCESSES AND IMPORTANCE OF ANTIOXIDANTS 2.1. Implication of oxidation processes in foods Foods contain lipids, proteins, saccharides, and vitamins that can be attacked by free radicals causing their oxidation. Oxidation, occurring especially in lipids and lipid-containing foods, is generally resulting in the deterioration

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in nutritional and sensory quality of foods. Therefore, it is a problem of great economic importance in the food production. Oxidation decreases the nutritional quality and safety after food processing and culinary use (deep-fried foods) by the formation of secondary reaction products in foods. The autoxidation of lipids in foods results in the formation of a very complex mixture of lipid hydroperoxides (LOOH) and chain-cleavage products. Oxidation is also responsible for the deterioration of sensory quality because of offensive rancid flavors’ and odors’ formation in lipids and lipid-containing products. During lipid oxidation, LOOH are readily decomposed into a wide range of carbonyl compounds, hydrocarbons, ketones, and other materials that contribute to flavor decline of foods. To estimate the flavor impact of volatile oxidation products, their relative threshold values must be considered together with their relative concentration in foods (Frankel, 1991). Lipid peroxidation may be initiated by any species that has sufficient reactivity to abstract a hydrogen atom from a polyunsaturated fatty acid side chain in membrane lipids (Aruoma, 1994). Lipid oxidation is defined by three stages. In the first stage (initiation), lipid radicals are formed; in propagation (second stage), the formation of hydroperoxides via peroxides is proceed; and in the last one (termination), hydroperoxides are reduced. The primary products of lipid oxidation of fatty acids, in the presence of initiator and oxygen, are LOOH. Depending on the conditions (temperature, traces of metal ions, pH, and presence of other components), the LOOH always undergo numerous secondary and tertiary reactions. Many of these reactions proceed again by free radical mechanisms involving peroxyl (LOO•), alkyl (L•), and lipid alkoxyl (LO•) radicals (Esterbauer, 1993). When free radicals and other reactive species extract a hydrogen atom from an unsaturated fatty acyl chain (e.g., polyunsaturated fatty acid), a carbon centered lipid radical (L•) is produced. This is followed by the addition of oxygen to L• to yield a lipid peroxyl radical (LOO•) that further propagates the peroxidation chain reaction by abstracting a hydrogen atom from a nearby unsaturated fatty acid. The resulting LOOH can easily decompose to form a lipid alkoxyl radical (LO•). This series of reactive oxygen species (ROS)initiated lipid-peroxidation reactions with the production of lipid peroxyl and alkoxyl radicals is called chain propagation (Fang, Yang, & Wu, 2002). Free radical autoxidation may be interrupted by several kinds of antioxidants. Antioxidants can act by the following mechanisms in lipid peroxidation (Dorman, Peltoketo, Hiltunen, & Tikkanen, 2003):

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– decreasing localized oxygen concentrations, – preventing chain initiation by scavenging initiating radicals, – binding catalysts, such as metal ions, to prevent initiating radical generation, – decomposing peroxides so they cannot be reconverted to initiating radicals, – chain breaking, to prevent continued hydrogen abstraction by active radicals. Antioxidants used in foods are chemical compounds that are capable to donate hydrogen radicals, so they could minimize rancidity and lipid peroxidation in food products. They enhance the shelf life of lipid-rich products without any damage to sensory or nutritional quality. Many experimental animal studies and biochemical researches point out the significance of lipid-oxidation products ingested with food for a health risk, as many lipid-oxidation products are known for interactions with biological materials to cause cellular damage. Formation of the LOOH and their secondary products during oxidation can reduce the vitamin and nutrient deficiency as lipid peroxides and free radicals destroy fat-soluble vitamins A and E and react with sulfur bonds in proteins so they decrease the protein quality due to the reduction in the sulfur amino acid content (Sanders, 1994). Oxidation products have also an effect on cardiovascular disease as many findings suggest that in vivo modification of low-density lipoprotein (LDL) by certain lipidperoxidation products, such as 4-hydroxynonenal and malonaldehyde, renders LDL more atherogenic and causes foam-cell formation (Esterbauer, 1993). Free radicals and ROS participate in tissue injuries and diseases such as cancer and other chronic diseases too. However, the oral toxicity of oxidized lipids is unexpectedly low. As reported by Esterbauer (1993) on basis of other several investigations (Kanazawa, Kanazawa, & Ntake, 1985; Oarada et al., 1988; Thompson & Aust, 1983), a possible explanation for the unexpectedly low acute toxicity of heavily oxidized oils and fats is that di- and polymeric-oxidation products are not well absorbed in the intestine and therefore do not reach the blood stream. Furthermore, peroxides are detoxified by glutathionedepended enzymes in the gut to less toxic lipid alcohols, which then appear in various organs. Based on some researches, Esterbauer (1993) also presents that heavily oxidized oils given orally are not acutely toxic, but upon chronic feeding of such foods, rats respond with growth retardation, intestinal irritation, enlarged liver and kidney, hemolytic anemia, increased serum concentrations of glutamate oxaloacetate transaminase and

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glutamate pyruvate transaminase, and decreased amounts of vitamin E in serum and liver. Chronic uptake of large amounts of heavily oxidized foods therefore can increase tumor frequency and incidence of atherosclerosis in animals. The endogenous body defense mechanisms (certain enzymes, vitamins, glutathione) can be overloaded by a high intake of reactive species, and the damage to cell structures, DNA, proteins, and lipids can occur (Frankel, 1991).

2.2. Importance of antioxidants for humans The origin of antioxidants dates back to antiquity. The ancient Egyptians demonstrated a remarkable technical knowledge by preserving dead bodies with plants whose extracts are rich in phenolic compounds. By the 1940s, free radical autoxidation reactions were elucidated and several chainbreaking antioxidants were identified. By the late 1950s, it was shown that oxidation reactions are involved in aging and the progression of several diseases and it was proposed that antioxidant molecules may slow down the aging process, disease progression, and prolong the life span (Gutteridge & Halliwell, 2010; Ndhlala, Moyo, & Van Staden, 2010). Antioxidants can be defined as substances that neutralize free radicals. To exogenous sources of free radicals besides foods belong tobacco smoke, burning of fossil fuels, certain pollutants such as ozone, further containing NO, nitrogen dioxide, and hydroxyl radicals, ionizing radiation, and pesticides. As endogenous source, there is the human body itself. Oxidative processes in humans are responsible for the formation of various forms of activated oxygen, the ROS. ROS are essential for energy maintenance, detoxification, and immune reactions that are continuously produced in the body. Free radicals, such as hydroxyl (OH•), superoxide (O2•
), alkoxyl (RO•), and peroxyl (RO2•) radicals, are molecules having an unpaired electron in the outer orbit, which are generally unstable and very reactive belong to the ROS. Hydrogen peroxide (H2O2) and singlet oxygen (1O2) are not free radicals but can lead to free radical reactions. The human body possesses defense mechanisms against ROS-induced damage, which include preventative mechanisms, repair mechanisms, physical defenses, and antioxidant defenses. Enzymatic antioxidant defense is provided by the enzymes catalase and glutathione peroxidase (both of which remove H2O2, as well as superoxide dismutase, which catalyzes the dismutation of O2
to form H2O2). Glutathione peroxidase is generally thought to be more important than catalase as a H2O2-removing system in humans (Aruoma, 1998). In addition, some low-molecular-mass

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substances, such as uric acid, ascorbate (vitamin C), glutathione, tocopherols (vitamin E), ubiquinol, ergothioneine, hypotaurine, and lipoic acid, may act as antioxidants in the human body. The imbalance between the generation of ROS and the activity of the antioxidant defenses causes “oxidative stress.” Severe oxidative stress can lead to mutation and mitochondrial and membrane disruption, and cause cell damage and tissue destruction. Therefore, when endogenous antioxidant defenses are inadequate for the purpose of scavenging the ROS completely, ongoing oxidative damage to DNA, lipids, proteins, and other molecules can be demonstrated (Aruoma, 1994). ROS have been implicated in the pathology of several human diseases, including atherosclerosis, inflammation, cancer, rheumatoid arthritis, and neurodegenerative diseases like Alzheimer’s disease and multiple sclerosis. However, ROS could contribute to the incidence to these diseases, they may not be the primary cause of these diseases. Several substances have been proposed to act as antioxidants in vivo. To that group belong substances such as b-carotene, uric acid, plant phenolics and flavonoids, ascorbic acid, and vitamin E. However, it is important to understand that in certain conditions, antioxidants can also act as prooxidants and stimulate free radical reactions.

3. ANTIOXIDANTS IN MEDICINAL PLANTS Numerous epidemiological studies have shown an inverse relationship between the intake of natural antioxidants from plant products and the incidence of some diseases because dietary plant antioxidants are capable of removing free radicals. Plant materials, such as medicinal plants (herbs, spices), could be promising sources of effective antioxidants. Among them, phenolic compounds, flavonoids and vitamins, exhibit potent antioxidant activities. Many constituents of plants may contribute to their antioxidant and other protective properties. To antioxidant components of medicinal plants belong especially phenolic antioxidants such as phenolic acids, flavonoids, terpenes, tocopherols, and vitamin C (ascorbic acid) and a group of carotenoids (b-carotene, etc.). Antioxidant components may act independently or more effectively in combination when synergism is manifested (together they have stronger effect) by a variety of mechanisms. The biological conditions in vivo in antioxidant determination may differ dramatically from in vitro experiment; therefore, caution must be taken when interpreting in vitro results and extrapolating to in vivo conditions (Dai & Mumper, 2010).

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3.1. Phenolic compounds Phenolic compounds are the most abundant secondary metabolites of plants. They are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants, with more than 8000 phenolic structures currently known. Plant phenolics are generally involved in defense against ultraviolet radiation or aggression by pathogens, parasites, and predators, as well as contributing to plants’ colors (Dai & Mumper, 2010). Increasing attention oriented to plant polyphenols is due to their perceptible antioxidant effects and has been associated with health promotion because of their antioxidant properties. They can act as reducing agents, hydrogen-donating antioxidants, singlet oxygen quenchers, and, in some cases, metal chelators. They interfere with the oxidation of lipids and other molecules by rapid donation of a hydrogen atom to radicals. Phenolics possess one or more aromatic rings, extended conjugated aromatic system to delocalize an unpaired electron, and one or more hydroxyl groups that are prone to donate a hydrogen atom or an electron to a free radical; therefore, they have ideal structure for free radical scavenging activities. The chemical structure of phenolic compounds affects their antioxidant effects, bioavailability, and specific interactions in organism metabolism. The main polyphenol dietary sources are fruits and vegetables, beverages (tea, juices, wine, coffee, and beer), legumes, and cereals. Medicinal plants, herbs, and spices could be relevant sources of phenolics in the diet too. Some studies present that the daily intake of phenolic compounds from plant foods range from about 20 mg to 1 g (Hertog, Hollman, Katan, & Kromhout, 1993). Nevertheless, these data were observed from the intake of foods such as fruits, vegetable, tea, and wine. No exact data are given for their intake from medicinal plants. Therefore, certain uncertainties about phenolic compounds remain due to the lack of exact comprehensive data not only about their content but also about their absorption and bioavailability. Data concerning the phenol content present that their maximum concentration in plasma rarely exceeds 1 mM after the consumption of 10–100 mg of a single phenolic compound. However, the total plasma phenol concentration is probably higher due to the presence of metabolites formed in the body’s tissues or by the colonic microflora (Scalbert & Williamson, 2000). Another major factor influencing their uptake may well be the interaction of these compounds with other molecular species such as proteins, arising from the fact that polyphenols are multidentate ligands able to bind simultaneously at more than one point to the protein surface (Rice-Evans, Miller, & Paganga, 1996).

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Additional important fact about phenols is that some phenolic antioxidants can, under certain conditions (high pH, high transition metal ions concentrations, and oxygen molecule presence), behave like prooxidants and initiate an oxidation process. Small-molecular weight phenolics (e.g., gallic acid) are easily oxidized and possess prooxidant activity. High-molecularweight phenolics, such as condensed and hydrolysable tannins, have little or no prooxidant activity (Hagerman et al., 1998). Plant phenolic compounds include phenolic acids, flavonoids, terpenes, tannins, stilbenes, and lignans. 3.1.1 Phenolic acids The antioxidant activity of phenolic acids and their esters depends on the number of hydroxyl groups in the molecule. Phenolic acids can be divided into two groups: • Derivatives of benzoic acid (gallic acid): The monohydroxybenzoates are effective hydroxyl radical scavengers, due to their propensity to hydroxylation and the high reactivity of the hydroxyl radical (Grootveld & Halliwell, 1986). • Derivatives of cinnamic acid (coumaric, caffeic, and ferulic acid): The hydroxycinnamic acids and coumaric, caffeic, and ferulic acids are produced from the shikimate pathway from L-phenylalanine or L-tyrosine. Caffeic acid (CA) is the most abundant phenolic acid, most often esterified with quinic acid as in chlorogenic acid (CHA) (Dai & Mumper, 2010). Hydroxycinnamic acid compounds occur most frequently as simple esters with hydroxy carboxylic acids or glucose, while the hydroxybenzoic acid compounds are present mainly in the form of glucosides. Furthermore, phenolic acids may occur in food plants as esters or glycosides conjugated with other natural compounds such as flavonoids, alcohols, hydroxyfatty acids, sterols, and glucosides (Herrmann & Nagel, 1989). Rosmarinic acid (RA) is the most predominant phenolic compound in numerous medicinal plant especially of Lamiaceae family (e.g., rosemary, basil, marjoram, thyme, balm, sage, mints). To other phenolic compounds present in the plants belong protocatechuic acid, p-hydroxybenzoic acid, gentisic, chlorogenic, syringic acids, caffeic, vanillic, and ferulic acids. Chen and Ho (1997) compared the antioxidative and free radical scavenging activities of CA, caffeic acid phenethyl ester (CAPE), ferulic acid (FA), ferulic acid phenethyl ester (FAPE), RA, and CHA with those of a-tocopherol and BHT. In the Rancimat test, the addition of test compounds in lard significantly extended the induction time of lipid oxidation,

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and the activities in decreasing order were CA  a-tocopherol > CAPE  RA > CHA > BHT > FA  FAPE. When the lipid substrate was changed to corn oil, the effectiveness of antioxidants on the induction time was obviously decreased, and the potency order of antioxidants was changed to RA > CA  CAPE  CHA > a-tocopherol > BHT; FA and FAPE had no significant antioxidative effect in the corn oil system. The DPPH scavenging activity of the test compounds was RA > CAPE > CA > CHA > a-tocopherol > FA > FAPE > BHT. The effect on retarding oil-in-water emulsion oxidation was BHT > CA > CAPE > RA > FA > CHA > a-tocopherol > FAPE. 3.1.2 Flavonoids Flavonoids are the most abundant polyphenols in our diets. The basic flavonoid structure is the flavan nucleus, containing 15 carbon atoms arranged in three rings (C6–C3–C6). Flavonoids are themselves divided into six subgroups: flavones, flavonols, flavanols, flavanones, isoflavones, and anthocyanins, according to the degree of oxidation (oxidation state) of the oxygen heterocycle, central third ring. Their structural variation in each subgroup is partly due to the degree and pattern of hydroxylation, methoxylation, or glycosylation (Dai & Mumper, 2010). Flavonoids occur in foods primarily as glycosides and polymers that are degraded to variable extents in the digestive tract. Although metabolism of these compounds remains elusive, enteric absorption occurs sufficiently to reduce plasma indices of oxidant status. The propensity of a flavonoid to inhibit free radical-mediated events is governed by its chemical structure. Since these compounds are based on the flavan nucleus, the number, positions, and types of substitutions influence radical scavenging and chelating activity. The diversity and multiple mechanisms of flavonoid action, together with the numerous methods of initiation, detection, and measurement of oxidative processes in vitro and in vivo, offer plausible explanations for existing discrepancies in structure–activity relationships. Despite some inconsistent lines of evidence, several structure–activity relationships are well established in vitro. Multiple hydroxyl groups confer upon the molecule substantial antioxidant, chelating, and prooxidant activity (Heim, Tagliaferro, & Bobilya, 2002). Also Van Acker et al. (1996) referred that for good scavenging activity, a catechol moiety on ring B is required. Flavonoids can interfere not only with the propagation reactions of the free radical but also with the formation of the radicals, either by chelating the transition metal or by

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inhibiting the enzymes involved in the initiation reaction. They also possess synergic effect with other antioxidants. Some of the most common flavonoids in medicinal plants include luteolin (flavone), apigenin (flavone), hispidulin (flavone), quercetin (flavonol), and kaempferol (flavonol). 3.1.3 Terpenes Terpenes form structurally and functionally different classes. They are made from combinations of several 5-carbon-base (C5) units called isoprene. The main terpenes in medicinal plants are the monoterpenes (C10) and diterpenes (C20). The monoterpenes are formed from the coupling of two isoprene units. They are the most representative molecules constituting 90% of the essential oils and allow a great variety of structures. Oxygenated compounds derived from these hydrocarbons include alcohols, aldehydes, esters, phenols, and oxides. It is estimated that there are more than 1000 monoterpene structures (Bakkali, Averbeck, Averbeck, & Idaomar, 2008). To the monoterpenes present in medicinal plants belong myrcene, terpinenes, p-cimene, menthol, a-terpineol, carvone, thymol, carvacrol, etc. The common diterpene in medicinal plants is carnosic acid, a diterpene phenol, which has a structure similar to RA. Carnosic acid is considered to be rather unstable, being degradated by oxidative hydroxylation to other phenolic compounds such as carnosol, a derivative with increased stability, while still possessing antioxidant properties, further rosmanol and epirosmanol (Bicchi, Binello, & Rubiolo, 2000). Almost all compounds presented in the essential oils such as monoterpenes and diterpenes possess antioxidant properties; the activity of cyclic monoterpene hydrocarbons with two double bonds is comparable to the activity of phenols. However, their antioxidant activities significantly differ due to their composition and oxidation of the components.

3.2. Vitamins To vitamins with antioxidant effect belong especially vitamin E (tocopherols) and also ascorbic acid (vitamin C). Tocopherols control ROS accumulation in plastids, thereby playing a major role in controlling singlet oxygen levels. a-Tocopherol affords protection to membranes mainly by quenching singlet oxygen and reacting with lipid peroxy radicals and has been shown to reduce the extent of lipid peroxidation in leaves and seeds (Asensi-Fabado & Munne´-Bosch, 2010).

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Plant tissues vary enormously in their vitamin E content and composition. Photosynthetic tissues generally contain low levels of vitamin E compared with seeds, which contain 10–20 times this level. Tocopherols are present in certain amount in medicinal plants such as fennel, cumin, and caraway. Ascorbate plays a prominent role in the antioxidant defense network of plants because of its excellent ability to scavenge ROS. It acts in coordination with glutathione and enzymatic antioxidants in chloroplasts, mitochondria, peroxisomes, and cytosol in the ascorbate–glutathione cycle to control the amount of hydrogen peroxide formed within the cell (Asensi-Fabado & Munne´-Bosch, 2010). Ascorbic acid is present in certain amount in some fresh medicinal plants such as fresh mints, lemon balm, oregano, and rosemary. Plants after drying process have considerably decreased (by 90%) level than that in the fresh plant (Capecka, Mareczek, & Leja, 2005). Ascorbic acid is a powerful synergist of tocopherols and other phenolic antioxidants.

3.3. Further antioxidants in medicinal plants Carotenoids control ROS accumulation in plastids, thereby playing a major role in controlling singlet oxygen levels. Carotenoids counteract the chlorophyll-photosensitized formation of singlet oxygen by intercepting (de-exciting or quenching) chlorophyll triplet states and singlet oxygen once formed (Asensi-Fabado & Munne´-Bosch, 2010). Carotenoids, particularly b-carotene, lutein, and zeaxanthin, are present in certain amount especially in some fresh medicinal plant such as mints, oregano, balm, basil, sage, rosemary, and thyme. Dry plants’ content of carotenoids is about half of the content in fresh ones (Capecka et al., 2005).

4. MEDICINAL PLANTS AS SOURCES OF ANTIOXIDANTS Medicinal plants are plants or parts of plants (leaves, flowers, seeds, rhizomes, roots, stems, and barks) used for therapeutic or medical benefit. Besides benefits for medicinal and pharmaceutical industry, they can be utilized in food industry (food antioxidants, antimicrobial components, functional food components, nutritional supplements, flavoring, and dyeing compounds), cosmetic industry (antioxidant and antimicrobial components, flavoring, and dyeing compounds), and perfumery (aroma compounds of essential oils), and also for culinary purposes. Antioxidants can be used in purely natural form isolated from medicinal plants, crude or processed by drying or by various extraction techniques such

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as extraction using polar and nonpolar organic solvents, steam distillation, or supercritical fluid extraction (SFE). Type and amounts of antioxidant compounds vary between different species, plant variety, environmental conditions, climatic differences, seasonal variations (Yesil-Celiktas et al., 2007), degree of ripeness, growing practices, geographical regions of growth (Yesil-Celiktas et al., 2007), and many other factors such as postharvest treatment and processing. In plant preparations (extracts, decoctions), the content and composition of antioxidants depend also on extraction technique, its conditions (extraction time and temperature), and solvents. Solvents such as methanol, ethanol, water, acetone, and their combinations are used often for the extraction of phenolics from plant materials. Polar solvents are supposed to be more effective in the extraction of lower molecular weight polyphenols, and acetone is applicable for the higher molecular weight compounds. Steam distillation and SFE produce essential oils containing volatiles responsible for the certain antioxidants and characteristic aroma. Even after the removal of volatile essential oils, aromatic plants may be dried, milled, and used as a source of natural antioxidants, either directly or after extraction (Pokorny´ & Korczak, 2001). For many purposes of industry, there is usage of antioxidants that are produced as nature-identical antioxidants (ascorbic acid, vitamin E in the form of a-tocopherol, and b-carotene). They have the same structure as that of natural compounds, but they are prepared synthetically. Pokorny´ and Korczak (2001) indicated that only slight progress may be expected in the preparation procedures for the isolation of natural antioxidants, excepting the use of supercritical carbon dioxide extraction of raw materials and that there will be a tendency for the application of whole plant materials without previous fractionation by extraction or other methods. As a novel type of extracts for applications in food or pharmaceutical industry, there could be used the de-odorized antioxidant-rich extracts, as medicinal plants have usually aromatic and pungent flavor; therefore, their direct use is limited to products that are usually seasoned (Chan, Iqbal, Khong, & Babji, 2011). However, certain medicinal plants that are known for strong medicinal benefits should not be used as food additives without previous detailed proof of their safety, especially in large additions. The antioxidant properties of plants such as medicinal plants, herbs, and spices have been widely studied. To commonly used medicinal plants with antioxidant activity known worldwide belong plants from several families, such as Lamiaceae (rosemary, sage, oregano, marjoram, basil, thyme, mints,

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lemon balm), Apiaceae (cumin, fennel, caraway), Zingiberaceae (turmeric, ginger), Ginkgoaceae (ginkgo), Asteraceae (chamomile), and Myrtaceae (eucalyptus), which were chosen for this review. The comparisons of the antioxidant activity between selected medicinal plants are shown in Section 5 (Table 3.1).

4.1. Lamiaceae family The family Lamiaceae (Labiatae) seems to be a rich source of plant species that possess antioxidant activity and have high concentrations of phenolic compounds. Because of these facts, Lamiaceae plants have been widely studied. However, each plant generally contains different phenolic compounds that possess various amounts of antioxidants and therefore different antioxidant capacities. As a strong chemotaxonomic marker for the subfamily Nepetoideae and Tribe Mentheae (Genus: Melissa, Mentha, Origanum, Rosmarinus, Salvia, Satureja, and Thymus), Tribe Lavanduleae (Genus: Lavandula), and Tribe Ocimeae (Genus: Ocimum) was observed a phenolic carboxylic acid, RA, an ester of CA, that is one of strong antioxidant components (Pedersen, 2000). To medicinal plants with antioxidant capacity from Lamiaceae family belong rosemary, sage oregano, marjoram, basil, thyme, mints, and lemon balm. 4.1.1 Rosemary (Rosmarinus officinalis) Rosemary exhibits the most effective activity among medicinal plants of Lamiaceae family. Its antioxidant capacity is related to the presence of antioxidants such as carnosic acid (Wellwood & Cole, 2004), carnosol, RA, rosmanol, isorosmanol, and epirosmanol. The exact composition and amount of various antioxidant components depend on the plant, its variety (clone) (Stefanovits-Ba´nyai, Tulok, Hegedu˝s, Renner, & Szo¨lloˆsi Varga, 2003), plant growth (del Ban˜o et al., 2003), degree of ripeness, climatic conditions, seasonal variations (Papageorgiou, Gardeli, Mallouchos, Papaioannou, & Komaitis, 2008; Yesil-Celiktas et al., 2007), and geographical regions of growth (Yesil-Celiktas et al., 2007). del Ban˜o et al. (2003) evaluated that the highest accumulation rate of antioxidants in rosemary was related with the young stages of plant development. RA showed the highest concentrations of all the polyphenols in all organs (leaves, flowers, stems, roots), and only in leaves, the main antioxidant compounds were present. The antioxidant activity of rosemary extracts depends for the great part on their phenolic composition. Antioxidants are generally isolated using various extraction methods with different

Table 3.1 Comparison of antioxidant activity of selected medicinal plants Method of AA determination

Type of extract

AA of medicinal plants

Source

Methanol

OV > RO > SO > OM > TV > OB > ZO > CL > CCy > FV

FRAP

Hossain, Brunton, Barry-Ryan, Martin-Diana, and Wilkinson (2008)

Methanol

RO > OV > TV > SO > OM > OB > CL > ZO > FV > CCy

TEAC

Hossain et al. (2008)

Essential oil

MC > OM

DPPH

Romeilah (2009)

De-odorized aqueous

RO > SO > OV > TV

DPPH

Dorman, Peltoketo, et al. (2003)

De-odorized aqueous

SO > OV > RO > TV

TEAC

Dorman, Peltoketo, et al. (2003)

Fresh and dry

MO ¼ MP > OV

DPPH

Capecka et al. (2005)

Methanol

OV > SO > TV ¼ RO > OB > ZO > CCy

TEAC

Shan, Cai, Sun, and Corke (2005)

Methanol

RO > TV > OV ¼ CL > SO > CCa > MO

TEAC

Wojdyło, Oszmia nski, and Czemerys (2007)

Methanol

TV > RO > OV > SO > CCa > CL > MO

FRAP

Wojdyło et al. (2007)

Methanol

RO > TV > CCa > CL > OV > SO > MO

DPPH

Wojdyło et al. (2007)

SCF-CO2

TV > RO ¼ SO

DPPH

Babovic et al. (2010)

Water infusion

MO > TV > MP > SO > OB > OM > MC > RO > FV

FRAP

Katalinic, Milos, Kulisic, and Jukic (2006) Continued

Table 3.1 Comparison of antioxidant activity of selected medicinal plants—cont'd Method of AA Type of extract AA of medicinal plants determination

Source

Water infusion

MS > OB

TEAC

Kiselova et al. (2006)

Water infusion

OV > MO > MP > MC

TEAC

Ivanova, Gerova, Chervenkov, and Yankova (2005)

Ethanol

OV > TV > OM

DPPH

Amarowicz et al. (2009)

Aqueous

SO > RO > OM > OB

SOD biosensor

Campanella, Bonanni, Favero, and Tomassetti (2003)

Essential oil

SO > RO

DPPH

Bozin, Mimica-Dukic, Samojlik, and Jovin (2007)

Essential oil

RO > CCy

DPPH

Gachkar et al. (2007)

Water infusion

OV > TV > MO > MP > MC > FV

DPPH

Burˇicˇova´ and Re´blova´ (2008)

Ethanol

TV ¼ MP > OV > MO > MC > FV

DPPH

Burˇicˇova´ and Re´blova´ (2008)

Water infusion

EG > MP > MC

DPPH

Atoui, Mansouri, Boskou, and Kefalas (2005)

Water infusion

OV > MO > MP > SO > OB > RO > OM

DPPH

Chrpova´ et al. (2010)

Hydrodistilled

OB > FV > CCy > ZO

DPPH

Hinneburg, Dorman, and Hiltunen (2006)

Methanol

RO > TV > FV > MP > EG

DPPH

Yoo, Lee, Lee, Moon, and Lee (2008)

Aqueous

OM > OV > TV ¼ RO > MP > OB > SO > GB > CCa > MO > MS > FV

ORAC

Zheng and Wang (2001)

Water infusion

OV > MO > MP > SO > RO

DPPH

Kwon, Vattem, and Shetty (2006)

Ethanol

OV > MP > RO > SO > MO

DPPH

Kwon et al. (2006)

Aqueous

FV > ZO > CL

TEAC

Cai, Luo, Sun, and Corke (2004)

Methanol

ZO > CL > FV

TEAC

Cai et al. (2004)

Aqueous

MO > MP > OV

DPPH

Lo´pez et al. (2007)

Methanol

MO > MP > TV > OV

DPPH

Lo´pez et al. (2007)

Ethanol

TV > MP > OV > MO

DPPH

Lo´pez et al. (2007)

RO, Rosmarinus officinalis; SO, Salvia officinalis; OV, Origanum vulgare; OM, Origanum majorana; TV, Thymus vulgaris; OB, Ocimum basilicum; MP, Mentha piperita; MS, Mentha spicata; MO, Melissa officinalis; CCy, Cuminum cyminum; FV, Foeniculum vulgare; CCa, Carum carvi; CL, Curcuma longa; ZO, Zingiber officinale; GB, Ginkgo biloba; MC, Matricaria chamomilla; EG, Eucalyptus globulus.

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conditions and solvent systems, using lipid solvents (e.g., hexane) and aqueous solvents (e.g., ethanol, methanol, and water) for classical extraction. To further techniques belong hydrodistillation to obtain essential oil (Carvalho, Moura, Rosa, & Meireles, 2005) followed by many studies with further improvements in separation techniques such as ultrasound sonification (Albu, Joyce, Paniwnyk, Lorimer, & Mason, 2004; Bicchi et al., 2000) and SFE (Babovic et al., 2010; Bicchi et al., 2000; Cavero et al., 2005) that are often used for antioxidants extraction. Carvalho et al. (2005) showed that rosemary extracts obtained by SFE exhibited larger amounts of antioxidant activities compared to the volatile oil (Wang, Wu, Zu, & Fu, 2008). Also enhancements of antioxidant capacity determination and antioxidant identification, by HPLC (Bicchi et al., 2000) and GC (Bozin et al., 2007; Carvalho et al., 2005), are further manifested. To commonly used commercial antioxidant extracts from medicinal plants in Europe belong especially extracts from rosemary as they are one of the most effective ones. They can be used as lipid antioxidants and metal chelators and are able to scavenge oxygen radicals. Extracts are available in various forms such as powder form, lipid or water-soluble extracts, and dispersed in water or oils. Rosemary extracts could be used as effective natural antioxidant agents to inhibit lipid oxidation and degradation of heme pigments caused by cooking and storage in processed meat (Ferna´ndez-Lo´pez et al., 2003). 4.1.2 Sage (Salvia officinalis) Sage is one of the largest members of the Lamiaceae, widespread throughout the world. The exact composition and amount of sage antioxidants depend, as mentioned above for rosemary, on the plant, its species (Bozan, Ozturk, Kosar, Tunalier, & Baser, 2002; Kamatou, Viljoen, & Steenkamp, 2010; Tepe, Sokmen, Akpulat, & Sokmen, 2006), and its characteristics (Farhat, Jorda´n, Chaouech-Hamada, Landoulsi, & Sotomayor, 2009). Antioxidant activity of sage is related with the presence of antioxidants such as carnosol, carnosic acid, rosmanol, and RA. RA has been reported as the one of the most responsible for the antioxidant activity (Cuvelier, Richard, & Berset, 1996). In supercritical fluid sage extract, epirosmanol and isorosmanol have been identified in great amount (Babovic et al., 2010). Another sage antioxidant, salvianolic acid L, which is a RA dimer, was isolated from S. officinalis and showed strong free radical scavenging activities for DPPH and superoxide anion radicals (Lu & Foo, 2001a). Capek, Machova´, and Turjan (2009) determined antioxidant activity of

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crude polysaccharides, presented in aerial parts of sage, in extracts with different effectiveness due to prepared fractions. Lu and Foo (2001b) determined the high superoxide dismutase activity of RAs that could be attributed to the radical scavenging catechols and the xanthine oxidaseinhibiting CA moieties contained in them. The antioxidant activity of the flavonoids was variable, and luteolin glycosides (with a catechol B-ring) were more active than apigenin glycosides (without a catechol B-ring). For isolation of sage antioxidants, various extraction methods especially with polar solvents (Grzegorczyk, Matkowski, & Wysoki nska, 2007; ¨ Pizzale, Bortolomeazzi, Vichi, Uberegger, & Conte, 2002), nonpolar solvents, hydrodistillation (essential oil), and SFE are used. 4.1.3 Oregano (Origanum vulgare) For the antioxidant activity of oregano is responsible antioxidants such as RA. The RA content in O. vulgare is approximately 5% (Ding, Chou, & Liang, 2010). Further in oregano, CA, flavonoids, and derivatives of phenolic acids and tocopherols are present as potent antioxidants. Another component exhibiting antioxidant activity is the rosmarinic acid methyl ester that may be exploited in the future to produce novel food additives (Ding et al., 2010). Matsuura et al. (2003) isolated water-soluble active components of dried leaves—oreganol-A (40 -O-b-D-glucopyranosyl30 ,40 -dihydroxybenzyl protocatechuate) and oreganol-B (40 -O-b-Dglucopyranosyl-30 ,40 -dihydroxybenzyl 4-O-methylprotocatechuate). The scavenging activity of oreganol-B was almost the same as that of quercetin and RA; oreganol-A is less potent antioxidant than another one. Cervato et al. (2000) showed that aqueous and methanolic extracts of oregano are effective in the inhibition of all phases of the peroxidative process (neutralizing free radicals—superoxide anion, hydroxyl radical, and DPPH; blocking peroxidation catalysis by iron through iron-chelating and iron-oxidizing properties; and interruption of lipid-radical chain reactions). Moreover, the amount of extract used in their study was far less than the amount of plant normally consumed in the Mediterranean diet. Dambolena et al. (2010) detected the changes of free radical scavenging activity in aqueous extracts of oregano, cultivated in different localities and conditions. They concluded that 70% of variability could be explained by the climate variables, and the temperature being the most important climatic variable. Herna´ndezHerna´ndez, Ponce-Alquicira, Jaramillo-Flores, and Legarreta (2009) detected that although ethanol oregano extracts contain high concentrations of phenols, mainly RA, high phenol concentration did not correlate with

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high antioxidant activity. Its effect on lipid oxidation is also related to the extraction and used solvent, the structure of the antioxidant compound, storage temperature, and initial oxidation state of the sample. S¸ahin et al. (2004) showed that also methanolic oregano extracts behaved as a strong free radical scavenger but was not effectively able to inhibit linoleic acid oxidation. They noted that most probably soluble phenolics are responsible for the radical scavenging activity of methanolic oregano extracts. Milos, Mastelic, and Jerkovic (2000) isolated volatile oregano aglycones, such as thymoquinone, further thymol and carvacrol. The aglycones and essential oil inhibited the formation of hydroperoxides more than a-tocopherol. Pure thymol, as the major component of the essential oil, and thymoquinone, as the major component among the aglycones, inhibited the formation of hydroperoxides less than a-tocopherol. Antioxidant activity of volatile aglycones was similar to those in essential oil where the presence of thymol and carvacrol is related to antioxidant effect (Yanishlieva, Marinova, Gordon, & Raneva, 1999). Faleiro et al. (2005) investigated that also oregano essential oil demonstrated protective antioxidant ability, being at higher concentrations as effective as BHT and better than BHA and a-tocopherol. Kulisic, Radonic, Katalinic, and Milos (2004) determined that the antioxidant activity of the oregano essential oil is less effective than the ascorbic acid but comparable with a-tocopherol and BHT. The synergy among minor oxygen containing compounds and antioxidant concentrations was suggested as possible factors, which influenced the antioxidant power of the oregano essential oil. 4.1.4 Marjoram (Origanum majorana, Majorana hortensis) Marjoram is a plant close to oregano in morphological classification that varies in a milder flavor. Marjoram plant and their extracts possess relatively strong antioxidant activity. It is due to several antioxidants such as highly labile carnosic acid, carnosol, followed by RA, CA, and flavonoids, luteolin-7-O-glucoside, apigenin-7-O-glucoside (Hossain et al., 2012). Marjoram contains a high amount of ursolic acid too. Another antioxidant found in marjoram is ursolic acid, a pentacyclic triterpenoid compound (Va´gi, Rapavi, et al., 2005; Va´gi, Sima´ndi, Suhajda, & He´thelyi, 2005). Va´gi, Rapavi, et al. (2005) and Va´gi, Sima´ndi, et al. (2005) investigated that the antioxidant activity of marjoram is significantly higher using polar solvent (ethanol) for the extraction than extracts prepared by n-hexane or supercritical CO2. Other observed differences in the antioxidant properties and amounts of phenolic compounds of marjoram were assessed to be

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caused by the geographic differences and therefore different climate features (e.g., higher numbers of sunny days). Romeilah (2009) investigated that the antioxidant activity of marjoram essential oil is mainly attributed to the major contents of terpinen-4-ol, g-terpinene, and a-terpineol. Marjoram essential oil also possesses radical scavenging activity. 4.1.5 Thyme (Thymus vulgaris) Antioxidants such as thymol and carvacrol, and their dimerization products— biphenyl compounds, further RA and flavonoids are responsible for the antioxidant activity of thyme. The major flavonoid in thyme evaluated by Justesen and Knuthsen (2001) was luteolin, which was present at the high level, followed by a small amount of apigenin. As investigated by Miura, Kikuzaki, and Nakatani (2002), the antioxidant activity of thyme antioxidants, with comparable activity to that of a-tocopherol, is considered to be due to the presence of ortho-dihydroxy groups. In volatile oil of thyme eugenol, thymol and carvacrol showed potent antioxidant activity. Their antioxidant activities were comparable to those of the known antioxidants, a-tocopherol and BHT (Lee, Umano, Shibamoto, & Lee, 2005). Simandi et al. (2001) assessed for thyme antioxidants isolation two extraction methods; ethanolic extract showed a slightly higher antioxidative effect than that obtained by SFE. 4.1.6 Basil (Ocimum basilicum) The antioxidant effect of basil depends on antioxidants such as RA, one of the main phenolic compounds and most potent basil antioxidant (Jayasinghe, Gotoh, Aoki, & Wada, 2003), CA, caffeoyl derivatives, and phenolic diterpenes. In addition, carvacrol present in essential volatile oil has antioxidant properties too. Catechin as a member of flavonoids is also potent antioxidant in basil (Surveswaran, Cai, Corke, & Sun, 2007). Javanmardi, Stushnoff, Locke, and Vivanco (2003) mentioned that basil possess valuable antioxidant properties. They evaluated a linear positive relationship between the antioxidant activity and total phenolic acids’ content. The antioxidant activity of phenolics is mainly due to their redox properties, which allow them to act as reducing agents, hydrogen donors, and singlet oxygen quenchers. However, as they indicated, antioxidant activity of basil may also come from the presence of other antioxidant secondary metabolites, such as volatile oils, carotenoids, and vitamins. Gu¨lc¸in, Elmastat, and Aboul-Enein (2007) referred that water and ethanol extract of basil have an antioxidant effect, which is concentration dependent. Both

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types of extracts had effective DPPH radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and reducing power and metal-chelating activities. The measured antioxidant capacity depended on the plant, its variety, and antioxidants presented in each extract due to solvent used. Hussain, Anwar, Sherazi, and Przybylski (2008) determined essential oils of basil collected in different seasons, with the result that antioxidant activity of the oils varied significantly, as seasons changed. Essential oils obtained from winter and spring crops showed greater radical scavenging activity than those collected during autumn and summer. Linalool, the major component of basil essential oil, exhibited lower antioxidant activity than the entire oil. The effectiveness of the essential oils toward the inhibition of peroxidation from winter and spring crops was comparable to BHT, whereas the values observed for summer and autumn samples were significantly lower than BHT. They also evaluated that samples collected in winter were richer in oxygenated monoterpenes, while those of summer were higher in sesquiterpene hydrocarbons. Leal et al. (2008) identified components in supercritical fluid basil extract as eugenol, tartaric acid, CA, quinic acid, caffeoylquinic acid, etc. Supercritical fluid extracts exhibited high antioxidant activity, compared to b-carotene, and can be used as a natural antioxidant with prolonged action, due to their stability. 4.1.7 Mint, peppermint, spearmint (Mentha officinalis, Mentha piperita, Mentha spicata) The genus Mentha covers approximately 25–30 species of which M. officinalis, M. piperita (peppermint), and M. spicata (spearmint) are the most known. These mint clones with antioxidant potential can be utilized as an effective, low cost source of natural commercial antioxidants for medicinal purposes and food industry too, how Kanatt, Chander, and Sharma (2007) showed for irradiated meat with mint extract addition. After 4 weeks of chilled storage, thiobarbituric acid-reactive substance values in irradiated meat containing mint extract (0.1%) were half of that in untreated irradiated meat. CA, eriocitrin (eriodictyol-7-O-rutinoside), luteolin-7-O-glucoside, and RA were identified as the dominant radical scavengers in water extracts by HPLC-DPPH• method by Kos¸ar, Dorman, Bas¸er, and Hiltunen (2004). Triantaphyllou, Blekas, and Boskou (2001) reported that water extracts from Mentha species contain bound phenolic acids and flavonoid derivatives such as CHA and 3- or 5-position hydroxylated glycosidic flavonoids. The results of the study of Elmastas¸, Dermirtas, Isildak, and Aboul-Enein (2006) indicated that also s-carvone, a main constituent of M. spicata essential oil,

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possesses high antioxidant activity compared to a-tocopherol. The watersoluble extracts from the Mentha species (M. aquatica, M. haplocalyx, M. dalmatica, M. verticillata, M. spicata, and M. piperita) demonstrated varying degrees of efficacy in antioxidant assays, with the M. piperita extract being better than the other extracts. As Dorman, Kos¸ar, Kahlos, Holm, and Hiltunen (2003) determined, the level of antioxidant activity was strongly associated with the phenolic content. Ahmad, Fazal, Ahmad, and Abbasi (2012) observed that methanolic extracts of Mentha species possess antioxidant capacity in the sequence: Mentha longifolia followed by M. officinalis and M. piperita, respectively. Fialova´, Tekel´ova´, Mrlianova´, and Grancˇai (2008) compared antioxidant activity of several mints (M. spicata, M. piperita, M. longifolia) harvested in two harvest times. They examined that the content of selected phenolic compounds was nearly always higher in the July harvest than in the September harvest. They established that the free radical scavenging activity of mint seemed to be attributed chiefly to the content of RA. The content of total hydroxycinnamic derivatives was higher in the July harvest, but the higher content of RA provided the small difference in scavenging concentration between the both harvest times. Arumugam, Ramamurthy, Santhiya, and Ramesh (2006) have studied antioxidant properties of four solvent fractions (hexane, chloroform, ethyl acetate, and water) of extract of dried leaves powder of M. spicata. The antioxidant activities of the solvent factions are closely related to the content of total phenolics present in them (less in hexane and chloroform fractions and highest in ethyl acetate and water fractions). Mentha extracts have antioxidant properties due to the presence of eugenol, CA, RA, and a-tocopherol. 4.1.8 Common balm, lemon balm (Melissa officinalis) To balm antioxidants belong components such as carnosic acid and triterpene acids—ursolic and oleanolic acids (Herodezˇ, Hadolin, Sˇkerget, & Knez, 2003). In addition, hydroxycinnamic acid derivatives and flavonoids with CA, m-coumaric acid, eriodictyol-7-O-glucoside, naringin, hesperidin, RA, naringenin, hesperetin, luteolin, and salvianic acid A are important for the lemon balm antioxidant capacity (Dastmalchi et al., 2008; Mencherini, Picerno, Scesa, & Aquino, 2007). Another phenolic compound, quercetin, had the highest antioxidant activity followed by gallic acid, quercitrin, and rutin (Pereira et al., 2009). Six major compounds of the lemon balm extract, namely, protocatechuic acid (3,4-dihydroxybenzoic acid), 2-(30 ,40 -dihydroxyphenyl)-1,3-benzodioxole5-aldehyde, CA, RA, caffeic acid methyl ester, and rosmarinic acid methyl

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ester, were isolated by Tagashira and Ohtake (1998). Among them, 2-(30 ,40 dihydroxyphenyl)-1,3-benzodioxole-5-aldehyde showed the most potent radical scavenging activity, about 10-fold that of ascorbic acid and of a-tocopherol. The compound had a characteristic 1,3-benzodioxole structure and was easily degraded into two molecules of protocatechualdehyde. The most powerful scavenging compounds of balm essential oil were determined monoterpene aldehydes and ketones (neral/ geranial, citronellal, isomenthone, and menthone) and mono- and sesquiterpene hydrocarbons (E-caryophyllene) (Mimica-Dukic, Bozin, Sokovic, & Simin, 2004). They presented that the balm essential oil exhibited very strong free radical scavenging capacity, reducing the DPPH radical formation, OH radical generation, and inhibition of lipid peroxidation, observed in a dose-dependent manner. Pereira et al. (2009) have demonstrated that aqueous, methanolic, and ethanolic extracts of lemon balm could protect food products against oxidative damage induced by various prooxidant agents that induce lipid peroxidation by different process. Among the purified compounds, quercetin had the highest antioxidant activity followed by gallic acid, quercitrin, and rutin. Balm extracts could therefore inhibit the generation of early chemical reactive species that subsequently initiate lipid peroxidation or, alternatively, they could block a common final pathway in the process of polyunsaturated fatty acids peroxidation. Koksal, Bursal, Dikici, Tozoglu, and Gulcin (2011) detected the antioxidant activity of balm plant phenolics in extracts obtained with two solvents, water and ethanol. Water extract was found to be more convenient solvent than ethanol extract for antioxidant activities. Fialova´ et al. (2008) compared antioxidant activity of balm harvested in two harvest times. The higher content of total hydroxycinnamic derivatives and the RA as well as stronger free radical scavenging activity were assessed in the July harvest time than in the September harvest. As they established free radical scavenging activity of balm was attributed chiefly to the content of RA. Dastmalchi et al. (2008) referred that balm extract is capable of scavenging a wide range of synthetic and naturally occurring free radicals. In the b-carotene-linoleic acid bleaching assay, which simulates biologically relevant medium, lemon balm extract showed exceptionally high antioxidant activity, superior to that of gallic and caffeic acids and statistically indistinguishable from quercetin and BHA. Marongiu et al. (2004) investigated that the antioxidant activity of lemon balm extract, obtained by using carbon dioxide under supercritical conditions, was not attributable to RA, since this did not found in the sample.

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Therefore, the antioxidant activity of balm SFE is probably depending on the presence of squalene and a-tocopherol (identified in the extract) and/or of other unidentified antioxidant compounds. In extracts from balm leaves of supercritical extraction, Ribeiro, Bernardo-Gil, and Esquı´vel (2001) detected no direct relation between antioxidant effect and total phenol content of the extract. They suggested that, in addition to the well-known antioxidants, other compounds are also able to act as antioxidants.

4.2. Apiaceae family Cumin, fennel, and caraway are common medicinal plants of the group of Apiaceae family known for their antioxidant potential. 4.2.1 Cumin (Cuminum cyminum) In cumin seeds, there are present antioxidants such as phenolic acids (CHA), flavanoids, and coumarins. In the essential oil, cumin aldehyde, cuminal, b-pinene, g-terpinene, and safranal are answerable for the antioxidant activity (Surveswaran et al., 2007). El-Ghorab, Nauman, Anjum, Hussain, and Nadeem (2010) found pinocarveol in the volatile cumin oil that could possess antioxidant capacity. Bettaieb et al. (2010) identified antioxidant components in cumin oils from roots, stems, leaves, and flowers, as g-terpinene, a-terpinene, and bornyl acetate, respectively. As the major phenolic compound in the roots, they found quercetin, whereas in the stems and leaves, p-coumaric, rosmarinic, trans-2-dihydrocinnamic acids, and resorcinol were predominant. Thippeswamy and Akhilender Naidu (2005) also showed that cumin is a potent antioxidant capable of scavenging hydroxy, peroxy, and DPPH free radicals and thus inhibits radical-mediated lipid peroxidation. They assessed as the most potent methanolic extracts that showed higher antioxidant activity compared with that of the aqueous extract. Three varieties of cumin, cumin (C. cyminum), black cumin (Nigella sativa), and bitter cumin (Cuminum nigrum), were investigated. Among the cumin varieties, bitter cumin (with high phenolic content) (Ani, Varadaraj, & Akhilender Naidu, 2006) showed the highest antioxidant activity followed by cumin and black cumin in different antioxidant systems. As Allahghadri et al. (2010) reported, the cumin essential oil showed higher antioxidant activity compared with that of BHT and BHA, probably due to high content of phenolic compounds, and the significant correlations that existed between phenolic content and antioxidant capacity. The radical scavenging effect of cumin essential oil was found to be three times more potent than the standard BHA and 4.8 times greater

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than BHT but less potent than Trolox. The cumin essential oil exhibited a dose-dependent scavenging of DPPH radicals. Bettaieb et al. (2010) mentioned that the essential cumin oils exhibited only moderate antioxidant activities in the different tests. However, El-Ghorab et al. (2010) determined that lower total phenolic content in the hexane extract of cumin, the DPPH method, and reducing Fe3 þ ions showed the high antioxidant activity for cumin essential oil. 4.2.2 Fennel (Foeniculum vulgare) To the important antioxidants of fennel belong phenolic acids (caffeoylquinic acid derivatives) and hydroxycinnamic acid derivatives, flavonols and flavones, and their glycosides, coumarins (Surveswaran et al., 2007). In the essential oil of fennel seeds, trans-anethol, fenchone, estragole, and limonene were identified as the major components. Therefore, due to the presence of these components, the fennel essential oil exhibited good DPPH radical scavenging activity and inhibition of peroxidation. The fennel seed extracts containing appreciable levels of total phenolic and flavonoid contents also showed good antioxidant potential (Anwar, Ali, Hussain, & Shahid, 2009). Oktay, Gu¨lc¸in, and Irfan Ku¨freviog˘lu (2003) determined the antioxidant activity of water and ethanol extracts of fennel seed. The extracts showed strong antioxidant activity—effective reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal-chelating activities. However, the scientists found no correlation between total phenolic content and antioxidant activity of fennel extracts. Conforti, Statti, Uzunov, and Menichini (2006) studied antioxidant activities of wild and cultivated F. vulgare seeds. The dissimilarity in the constituents, and thus in biological activity, between the wild and cultivated plants correlates with the different ecological conditions in which they grow. Total phenolic contents differed among plant extracts, contributing to different antioxidant activities. Shahat et al. (2011) examined essential oils of the fennel fruits of three organically grown cultivars for antioxidant activities. They assessed greatly different percentages of major, highly abundant, monoterpenoids (trans-anethole, estragole, fenchone, and limonene) in all three cultivars in each oil and therefore dissimilar antioxidant activities of the essential oils. According to Singh, Maurya, de Lampasona, and Catalan (2006), both the F. vulgare volatile oil, with the major component trans-anethole, and its acetone extract showed strong antioxidant activity in comparison with butylated hydroxyanisole and butylated hydroxytoluene. In addition, fennel shoots, leaves, and steams also

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possess the antioxidant potential that was measured by Barros, Heleno, Carvalho, and Ferreira (2009). They evaluated differences, which were particularly related to their composition in antioxidant compounds such as vitamins (ascorbic acid and tocopherols) and phenolics. The shoots seemed to have the highest radical scavenging activity and lipid peroxidation inhibition capacity, which is in agreement with the highest content in phenolics, ascorbic acid, and tocopherols. 4.2.3 Caraway (Carum carvi) Thymol, carvacrol, and flavonoids belong to compounds responsible for the antioxidant capacity of caraway. In the study of Bamdad, Kadivar, and Keramat (2006), five different model systems clearly showed that antioxidant activity of phenolic compounds presented in caraway methanolic extract is comparable with those of BHT. Results indicated that extracted phenolics were able to change redox condition of metals and therefore lessen their catalytic activity. Chain breakdown of oxidation reaction through the reduction of free radicals by phenolics was also evidenced. Caraway extract also showed the ability to chelate free radicals. Regarding their activity in food, phenolic extract of caraway, although at slightly higher concentration, was comparable with BHT, and therefore, they can be useful in food applications. Samojlik, Lakic´, Mimica-Dukic´, Ðakovic´-Sˇvajcer, and Bozˇin (2010) tested essential caraway oil and determined that the oil was able to reduce the stable DPPH• in a dose-dependent manner and to neutralize H2O2. Caraway essential oil also strongly inhibited lipid peroxidation. As the most active compounds of C. carvi essential oil, there were identified trans-anethole and certain monoterpene alcohols (carveole and its isomers).

4.3. Zingiberaceae family Major common commercially cultivated species of Zingiberaceae family, valuable especially for their rhizomes, are Curcuma longa, turmeric, and Zingiber officinale, ginger, that were used for different purposes for over 2000 years. 4.3.1 Turmeric (C. longa) Rhizomes of turmeric contain several curcuminoids such as phenolic compounds, curcumin, bisdemethoxycurcumin, and demethoxycurcumin (Chainani-Wu, 2003), and also ferulic acid and p-coumaric acid (Kumar, Nayaka, Dharmesh, & Salimath, 2006) as potent antioxidants. Singh,

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Kapoor, et al. (2010) showed that a-turmerone, a major component in fresh rhizomes, is only minor one in dry rhizomes, and the content of b-turmerone in dry rhizomes is less than a half amount found in fresh rhizomes. Ak and Gu¨lc¸in (2008) determined the antioxidant activity of curcumin (diferuoyl methane), a major component of C. longa. It was found to be an effective antioxidant in different in vitro assays including reducing power, radical scavenging, hydrogen peroxide scavenging, and metal-chelating activities, when compared to standard antioxidant compounds such as BHA, BHT, a-tocopherol, and Trolox. It had a marked antioxidant effect in linoleic acid emulsion. Reactive radical scavenging and antioxidant activity of curcumin were interpreted as originating by H-atom abstraction from the free hydroxyl group. They concluded that it was H-atom donation from phenolic group, which was responsible for the “superb antioxidant” properties of curcumin. Masuda et al. (2001) studied an antioxidant mechanism of curcumin in polyunsaturated lipids. From the structure of the isolated compounds, they evaluated that curcumin showed a chain-breaking antioxidant activity with the termination reaction by the coupling of antioxidant radical and another radical species. As they referred when curcumin exists in the presence of an unsaturated lipid, the lipid hydroperoxyl radical acts as radical species and forms several isomeric hydroperoxides by coupling reaction. The hydroperoxides then react intramolecularly to produce and accumulate the characteristic tricyclic compounds in the system. Jayaprakasha, Rao, and Sakariah (2006) studied antioxidant capacities of individual curcuminoids of turmeric by in vitro model systems. In comparison with butylated hydroxyl toluene, the antioxidant activity was found to be highest with curcumin, followed by demethoxycurcumin and bisdemethoxycurcumin. Pozharitskaya, Ivanova, Shikov, and Makarov (2008) mentioned in their study the same sequence of antioxidant potential of turmeric curcuminoids: curcumin > demethoxycurcumin > bisdemethoxycurcumin  ascorbic acid. Singh, Kapoor, et al. (2010) determined the antioxidant properties of the essential oil and ethanol oleoresin of fresh and dry rhizomes of turmeric. The higher antioxidant properties of the essential oil and oleoresin in turmeric were observed for fresh rhizomes, containing aromatic turmerone, a-turmerone, and b-turmerone as the major constituents, as compared to dry ones. Braga, Leal, Carvalho, and Meireles (2003) determined turmeric extracts obtained using various techniques such as hydrodistillation, lowpressure extraction with ethanol and isopropanol, Soxhlet extraction, and supercritical CO2 extraction. The maximum amount of curcuminoids was obtained by Soxhlet extraction with the mixture of ethanol and isopropanol.

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The Soxhlet extract and low-pressure extract exhibited the strongest antioxidant activities. 4.3.2 Ginger (Z. officinale) Gingerol-related compounds such as gingerols, shogaols, gingediols, zingerone, dehydrozingerone, gingerinone, and diarylheptanoids contribute to the antioxidant capacity of ginger rhizomes (Masuda, Kikuzaki, Hisamoto, & Nakatani, 2004; Surveswaran et al., 2007; Tao et al., 2008; Zancan, Marques, Petenate, & Meireles, 2002). Singh et al. (2008) and El-Ghorab et al. (2010) found geranial, camphene, p-cineole, a-terpineol, zingiberene, and pentadecanoic acid as the major components in essential oil; eugenol in ethanol oleoresin, while in the methanol, CCl4, and isooctane oleoresins, zingerone was the major component. Zancan et al. (2002) investigated the influence of the temperature and the interaction of the pressure and the solvent. Their results showed that all studied factors significantly affected the total yield and the amounts of the major substances present in the ginger extracts such as zingiberene, gingerols, and shogaols. The antioxidant activity of the ginger extracts remained constant at 80% and decreased to 60% in the absence of gingerols and shogaols. Eleazu and Eleazu (2012) studied antioxidant potentials of six varieties of ginger. All the varieties were observed to possess strong antioxidant activities and had high quantities of phenols, which may be responsible for their antioxidant activities. Correlation analysis in the study revealed that the total phenolic contents of the ginger varieties correlated negatively with their total oleoresin contents. This finding suggested that the oleoresin contents might not have come from their phenolics constituents and that the oleoresins present could have little contribution to the antioxidant activities of the ginger varieties. Masuda et al. (2004) analyzed an antioxidant activity of gingerol-related compounds isolated from the dichloromethane extract of the ginger rhizomes. Gingerols, shogaols, gingerdiols, gingerdiones, and dehydrogingerdiones (with an alkyl group bearing 10-, 12-, or 14-carbon chain length) showed antioxidant activity. Their results suggested that the substituents on the alkyl chain might contribute to both radical scavenging effect and inhibitory effect of autoxidation of oils. Stoilova, Krastanov, Stoyanova, Denev, and Gargova (2007) evaluated the antioxidant effect of ginger and its CO2 extract. It manifested a very good scavenging of DPPH and reduced its reducing capacity. The extract could be used as an antioxidant at an earlier stage of fat oxidation. The polyphenols in the ginger extract

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also demonstrated a higher chelato-forming capacity with regard to Fe3 þ, leading to the prevention of the initiation of hydroxyl radicals which are known inducers of lipid peroxidation. The ginger extract showed an antioxidant activity comparable with that of BHT in inhibiting the lipid peroxidation, most inhibited was the stage of formation of secondary products of the autoxidation of fats. El-Ghorab et al. (2010) observed difference between the chemical composition and antioxidant capacity of essential oils of fresh and dried ginger; however, DPPH and ferric reducing/antioxidant power (FRAP) method showed the antioxidant activity in both ginger essential oils.

4.4. Ginkgoaceae family To the last remaining member of Ginkgoaceae family with potent antioxidant capacity belongs ginkgo that is used therapeutically for centuries, especially in traditional Chinese medicine. 4.4.1 Ginkgo (Ginkgo biloba) To the antioxidant constituents of ginkgo appertain phenolic acids that, according to Ellnain-Wojtaszek, Kruczy nski, and Kasprzak (2003), possess weaker antioxidant activity than polyhydroxy-phenolic acids. Thus, protocatechuic acid (two o-hydroxy groups) had higher antioxidant potential than p-coumaric acid (phenolic acid). To the group of ginkgo antioxidants belong CHA, coumarins, catechin hydrate, rutin, and quercetin (Maltas & Yildiz, 2012); in essential oil, there are cumin aldehyde, cuminal, and safranal. Tang, Lou, Wang, Li, and Zhuang (2001) studied coumaroyl flavonol glycosides of ginkgo leaves. Several of them, such as quercetin 3-O-a-L-[6000 -pcoumaroyl-(b-D)-glucopyranosyl-(1,2)-rhamnopyranoside] and kaempferol 3-O-a-L-[6000 -p-coumaroyl-(b-D)-glucopyranosyl-(1,2)-rhamnopyranoside]7-O-b-D-glucopyranoside, showed profound antioxidant activities in DPPH and cytochrome c reduction assays. Maltas, Vural, and Yildiz (2011) determined that the methanolic extract of G. biloba possesses a more effective antioxidant capacity than the acetone extract, depending on the solvent effect. High total phenolic content of the methanolic extract is moderately to highly associated with the antioxidant properties. It is considered that also fatty acid composition and high content of EPAs have an effect on the antioxidant activity of G. biloba. Maltas and Yildiz (2012) evaluated different extracts of G. biloba leaves. Their results indicated that methanolic extract of ginkgo had stronger antioxidant activity than acetone and hexane extracts and also highest phenolic and flavonoid contents. Goh, Barlow, and Yong (2003) evaluated appropriate

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conditions for ginkgo infusions’ preparation to obtain the highest antioxidant capacity. They shown that larger surface area of leaves, high infusion temperature, and an infusion time around 10–15 min gave the highest antioxidant capacity of ginkgo leaves. Zahradnı´kova´, Schmidt, Sekreta´r, and Jana´cˇ (2007) investigated the antioxidant activity of G. biloba’s active compounds by addition of extract into vegetable oils (sunflower and rapeseed oils). The ethanol extract of ginkgo leaves demonstrated an antioxidant activity, but it was lower than the antioxidant activity of commercial extract and BHT. Goh and Barlow (2002) mentioned the loss of antioxidant capacity in ginkgo nuts over the first 10 min of heating. This was most likely due to the loss of a heat-unstable vitamin C. A substantial amount of antioxidant capacity still remained in the nuts, which could be due to heat-stable water-soluble compounds such as polyphenols.

4.5. Asteraceae family To the common medicinal plant of Asteraceae family with potent antioxidant capacity belongs chamomile. 4.5.1 Chamomile (Matricaria chamomilla) For the antioxidant activity of chamomile essential oil is responsible especially sesquiterpenes, and some monoterpenes too. The highest concentrations were calculated for chamazulene, a-bisabolol, and bisabolol oxide A (appreciatively the same concentration for each component) (Costescu et al., 2008). In addition, guaiazulene was identified in the essential oil (Romeilah, 2009). Chamazulene exerts antioxidant effects through the inhibition of lipid peroxidation and blocks chemical peroxidation of arachidonic acid for antioxidant effects. It was found that guaiazulene could inhibit lipid peroxidation very significantly, and can scavenge hydroxyl radicals and interact with DPPH. Also essential chamomile oil showed good antioxidant capacities compared with vitamin C (Romeilah, 2009). Also Owlia, Rasooli, and Saderi (2007) referred that essential oil from chamomile showed good antioxidative potential. Abdoul-Latif et al. (2011) determined that chamomile essential oil and methanol extract inhibited the oxidation in the b-carotene-linoleic acid system effectively. When compared to BHT, the essential oil and methanol extracts were nearly the same value. Sazegar et al. (2010) determined the antioxidant activity of chamomile ethanol extract, also in fat-containing foods (sunflower oil). The antioxidant activity was valuable and rose by increasing the extraction oil concentrations due to presented antioxidants.

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4.6. Myrtaceae family There are over several hundred species of eucalyptus plants. Barks, roots, fruits, buds, leaves, and other parts of plant are considered as source of essential aromatic oils to cure several ailments. 4.6.1 Eucalyptus (Eucalyptus globulus) For the antioxidant activity of eucalyptus is responsible antioxidative polyphenol oenothein B, hydrolyzable tannin dimer, gallic acid and ellagic acid, further in the eucalyptus leaves extract there were found 3-O-b-Dglucuronides of quercetin and kaempferol (Amakura, Yoshimura, Sugimoto, Yamazaki, & Yoshida, 2009). Mishra et al. (2010) analyzed the essential oil extracted from the eucalyptus leaves. Phytochemical screening showed the presence of flavonoids, terpenoids, saponins, and reducing sugars. The presence of flavanoid constituent upon phytochemical screening enhanced the chances of antioxidant activity. Eucalyptus is not having any cardiac glycosides and anthraquinones. The free radical scavenging activity of the different concentrations of the leaf oil increased in a concentrationdependent fashion. Lee and Shibamoto (2001) analyzed volatile oils of E. globulus and Eucalyptus polyanthemos leaves. They assessed that E. polyanthemos inhibited the oxidation more effectively, with the identified constituents of thymol, 1,8-cineole, benzyl alcohol, and terpinen-4-ol.

5. ANTIOXIDANT ACTIVITY OF MEDICINAL PLANTS The antioxidant properties of plants, such as medicinal plants, herbs, and spices, and their constituent compounds have been widely studied. The research in this area has been led at least partially by several branches of industry seeking for natural protecting compounds. The antioxidant activity (AA) of medicinal plants depends on each plant (variety, environmental conditions, harvesting methods, postharvest treatment, and processing), and composition and concentration of present antioxidants. For appropriate determination of antioxidant capacity, the extraction technique, its conditions, solvent used, and particular assay methodology are important. Extracts from natural plant materials are mixtures of many components. In many research studies concerning determination of antioxidant activity, the correlation between antioxidant capacity results and phenolics concentration was observed (e.g., Katalinic et al., 2006). The results also depend on the chemical nature and structure of the phenolic compounds present in the

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extracts. In many assays, extracts with higher total phenolic contents were noticeable in antioxidant activity (Dorman, Peltoketo, et al., 2003). However, in some cases, the content of major antioxidants (phenolic compounds) was rather low, a synergy can occur between them, and therefore, the other minor plant constituents might significantly influence the differences in their overall antioxidant activity (Kulisic et al., 2004). Influence of drying process of medicinal plants is also the important factor for the antioxidant potential. Cousins, Adelberg, Chen, and Rieck (2007) assessed that drying of fresh plant tissue reduced the ability of extracts to scavenge the DPPH radical. It has been mentioned that many inherent variations in commercial processes including variation in drying techniques could lead to quality differences in the final products. However, in the study of Capecka et al. (2005), fresh and dry extract of some medicinal plants showed similar values of antioxidant capacity. Antioxidants are generally isolated using various extraction methods. The most used solvents for classical extraction are polar ones (e.g., ethanol, methanol, and water) or lipid solvents (e.g., hexane). Polar solvents are generally supposed to be more effective in the extraction of lower molecular weight polyphenols (Grzegorczyk et al., 2007; Pizzale et al., 2002), whereas acetone is rather applicable for the higher molecular weight compounds. Further hydrodistillation (essential oil) and techniques based on the use of compressed fluids as extracting agents, such as subcritical water extraction, SFE (Babovic et al., 2010; Bicchi et al., 2000; Cavero et al., 2005), pressurized fluid extraction, or accelerated solvent extraction, produce essential oils containing volatiles responsible for the certain antioxidants. Ultrasound sonification (Albu et al., 2004) is another method used for antioxidants isolation. Cervato et al. (2000) showed that water and methanol were effective solvents to obtain higher antioxidant potential of medicinal plant extracts. Arumugam et al. (2006) studied antioxidant properties of four solvent fractions (hexane, chloroform, ethyl acetate, and water) of extracts. They investigated that antioxidant activities of the solvent factions were closely related to the content of total phenolics present in them. Less amount of phenolic compounds was found in hexane and chloroform fractions; the highest values were extracted in ethyl acetate and water fractions. Va´gi, Rapavi, et al. (2005) and Va´gi, Sima´ndi, et al. (2005) investigated higher antioxidant activity with polar solvent (ethanol) extraction than in extracts prepared by n-hexane or supercritical CO2. Carvalho et al. (2005) showed that supercritical fluid extracts exhibited larger amounts of antioxidant activities compared to the volatile oil.

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5.1. Determination of antioxidant activity The antioxidant activity (total antioxidant capacity) of plants and plant extracts can be determined by several in vitro methods. There are two general types of assays widely used for different antioxidant studies. To the first group belong assays that are associated with electron or radical scavenging, including the DPPH assay, Trolox equivalent antioxidant capacity (TEAC) assay, and FRAP assay. They are based on reduction reaction. Other ones are assays associated with lipid peroxidations, including the thiobarbituric acid assay and b-carotene bleaching assay (Moon & Shibamoto, 2009). The DPPH assay is used to predict antioxidant activities by mechanism in which antioxidants act to inhibit lipid oxidation, so scavenging of DPPH radical and therefore determinate free radical scavenging capacity. The method is widely used due to relatively short time required for the analysis. The DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical is very stable, reacts with compounds that can donate hydrogen atoms, and has a UV–vis absorption maximum at 515 nm. The method is based on the scavenging of DPPH by antioxidants, which upon a reduction reaction decolorizes the DPPH methanol solution. The assay measures the reducing ability of antioxidants toward the DPPH radical. The TEAC assay is also widely used to measure total radical scavenging capacity. The assay is based on the discoloration of a preformed ABTS (2,20 -azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) radical by antioxidant compounds, thus reflecting the amount of ABTS radicals that are scavenged within a fixed time period in relation to that of Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid). Total radical scavenging capacity of the sample is calculated by relating the decrease in absorbance to Trolox absorbance at 734 nm. A limitation of this method is that the TEAC value characterizes the capability of test extracts to react with the ABTS radical rather than to inhibit the oxidation process. The FRAP determination (ferric reducing antioxidant power) is used to measure antioxidant power of plant extracts in their ability to reduce Fe3 þtripyridyltriazine to Fe2 þ-tripyridyltriazine. The assay is based on electrontransfer reactions in which a ferric salt potassium ferricyanide is used as an oxidant. The reaction mechanism involves the reduction of ferric 2,4,6tripyridyl-s-triazine to the colored ferrous form. The absorption wavelength is 593 nm. The ORAC (oxygen radical absorbance capacity) assay uses the fluorescent b-phycoerythrin (B-PE) as an oxidizable protein substrate (probe) and AAPH (2,20 -azobis(2-amidinopropane) dihydrochloride) to generate peroxyl radicals. However, B-PE is photobleached under fluorescence plate-reader conditions and reacts with phenolic compounds due to nonspecific protein

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binding. Added antioxidants compete with the substrate for the peroxyl radicals, thereby inhibiting or retarding fluorescein oxidation. The substrate (fluorescein) decays in the presence of peroxyl radicals that are generated at a controlled rate by thermal decomposition of AAPH in an air-saturated solution. The fluorescence intensity is measured at the emission wavelength of 525 nm with extinction at 485 nm. In the ORAC reaction, as fluorescein is consumed, its fluorescence intensity decreases. The ORAC assay also measures both hydrophilic and lipophilic chain-breaking antioxidant capacity (Ndhlala et al., 2010). In lipid peroxidation inhibition capacity assay, thiobarbituric acid-reactive substances are used for inhibition of lipid peroxidation. Also new methods of the determination of antioxidant activity are developing constantly. Brainina, Ivanova, Sharafutdinova, Lozovskaya, and Shkarina (2007) introduced potentiometry method that is in good correlation with some common methods of antioxidant activity assay (DPPH, TEAC). The comparison of the antioxidant activity of selected medicinal plants extracts (various solvents, isolation and determination methods) is presented in Table 3.1.

6. PROTECTING HEALTH EFFECTS OF MEDICINAL PLANTS Medicinal plants and their products are used worldwide for thousands of years due to their health effects (anti-inflammatory, antioxidant, antibacterial, digestive, antispasmodic, cholagogue, carminative, diuretic, hypolipidemic, sedative, enhancing the function of the immune system as well as anticancer, antitumor activity, etc.) and a key role in preventing various diseases such as cardiovascular diseases, gastrointestinal disorders, inflammatory diseases, and cancer initiation. According to WHO, as many as 80% of the world’s people rely on traditional medicine for their primary health-care needs (WHO, IUCN, & WWF, 1993). Common medicinal plants are used in folk medicine because many of them are proved as effective remedies against certain ailments. Whereas they are generally considered to be safe and contain biologically active constituents that have beneficial physiologic effects, some plants are safe in modest amounts but they may show some adverse effects from their usage or become toxic at higher doses; other are known to be lethal (Craig, 1999). Medicinal plants, parts of these plants, and their preparations are usually complex mixtures of numerous active compounds with health effects that are concentration dependent. Biologically active substances in plants could

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often cooperate to show synergism, and therefore, the advantage of their usage is that also minor constituents can contribute to the overall quality. Although there are concentrated sources of many phytochemicals, as well as some core nutrients, medicinal plants are usually consumed only in small quantities, so their dietary contribution is relatively small and insufficient to show medicinal effects. However, if eaten regularly, medicinal plants in the form of some preparations, herbs and spices could provide useful amounts of beneficial bioactives, including both ubiquitous and less common phytochemicals (Hedges & Lister, 2007). Moreover, in the majority of studies presented in the literature, only the main constituents were analyzed. To be able to act as effective constituents in vivo, these substances should be found in adequate amounts in the body, meaning that they should be absorbed from the gastrointestinal tract, circulate in the blood and not be immediately metabolically deactivated (Dorman, Peltoketo, et al., 2003). Another relevant problem in interpreting epidemiologic data is that there is often difficult to distinguish whether the protective effects are due to antioxidant nutrients or other constituents in the diet as plant products contain many potential antioxidants not only the established ones but also others lesser known but with potentially great significance. Probably the most studied, known and popular health benefit of common medicinal plants is their antimicrobial effectiveness. To the requested medicinal influences presently belong also positive effects on cardiovascular diseases and on cancer initiation. However, many other positive effects of medicinal plants (e.g., digestive and anti-inflammatory) on good health conditions are also quite familiar.

6.1. Antimicrobial effect There is still increasing interest in antimicrobial effects of medicinal plants and their products due to the food microbial safety to reduce the occurrence of microbial (Gþ and G
bacteria, yeast, fungi) contamination in foods caused by undesirable pathogenic microorganisms such as Listeria monocytogenes, Escherichia coli O157:H7, Salmonella typhimurium, Bacillus cereus, and Staphylococcus aureus. Antimicrobially acting compounds and extracts improve shelf life of foods and generally could minimize pathogens and toxins produced by microorganisms. There are more than 1340 plants with defined antimicrobial compounds, and over 30,000 components have been isolated from phenol groupcontaining plant–oil compounds and used in the food industry (Tajkarimi, Ibrahim, & Cliver, 2010).

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Plants are rich in a wide variety of secondary metabolites, such as phenols, terpenoids, sesquiterpenes, hydrocarbons, flavonoids, tannins, acids, alcohols, aldehydes, and alkaloids, which have been found to have antimicrobial properties in in vitro studies. Also minor components play an important part for antimicrobial activity, possibly by producing a synergistic effect between other components. However, well, these compounds or their extracts act antimicrobially in vitro, to achieve the same effect in foods, their greater concentration is needed. Especially the form of essential oil, the aromatic oily liquid, is responsible for antimicrobial activities of medicinal plants, which is effective against microbial deterioration. Supercritical fluid extracts, methanolic and ethanolic extracts, and water extracts are also utilized, but generally less effective. The effectiveness of these extracts in foods depends on many factors such as the pH values, the storage temperature, the amount of oxygen and the composition, and concentration of active components too. However, commercially useful characterizations of preservative properties are available for only a few essential oils. Commercially based plant-origin antimicrobials are most commonly produced by steam distillation and hydrodistillation methods. Alternative method is SFE using carbon dioxide under high pressure and low temperature that provide higher solubility and improved mass transfer rates. Moreover, the manipulation of parameters such as temperature and pressure leads to the extraction of different components when a particular component is required (Tajkarimi et al., 2010). Only a few food preservatives containing essential oils are already commercially available. The most common medicinal plants in these products are rosemary, sage, thyme, oregano, basil, caraway, cumin, turmeric, ginger, and fennel, which are known for their potent antioxidant and antimicrobial (bacteriostatic) activities. They have been successfully used alone or in combination with other preservation methods. Antimicrobial activity against common Gþ and G
bacteria, yeast (Candida albicans), and fungi of selected medicinal plants in different forms is presented in Table 3.2.

6.2. Anticancer effect The medicinal plants’ research is presently intensively focused also on the identification of naturally occurring anticarcinogens, which were found in certain plants. The interest in these natural medicines is mainly due to the fact that diseases such as cancer are still difficult to cure. Therefore, there is a great scientific effort to delay the process of carcinogenesis and to reduce the morbidity and mortality of cancer. In addition, the usage of potent

Table 3.2 Antimicrobial activity of selected medicinal plants Antimicrobial activity Medicinal plant

-a Gþ bacteria

G
bacteria

Yeast Fungi

Source

EC, SaE, SS, ST

CA

Bozin et al. (2007)

2 BC, SA

EC, PA

CA

Genena, Hense, Smania Junior, and de Souza (2008)

1 BS, MF, SA, SE, SL

EC, SaE, SS, ST

CA

Bozin et al. (2007)

1 BC, BMe, BS

KO

Rosmarinus officinalis 1 BS, MF, SA, SE, SL

Salvia officinalis

Origanum vulgare

Origanum majorana

Thymus vulgaris

Ocimum basilicum

1 BM, BS, EF, SA, SP EC, PV

Delamare, Moschen-Pistorello, Artico, Atti-Serafini, and Echeverrigaray (2007) CA

S¸ahin et al. (2004) AA, AF, AV, FA, FO, FS, FT, P, R

1 BS, SA

EC, PA, STm

Sivropoulou et al. (1996)

2 BC

EC, PF

1 BS, EF, SA, SM

EC, KP, S, SC, SF

Busatta et al. (2008)

1 LM, SA

EC, SaE, SF, SS, STm, YE

Rota, Herrera, Martı´nez, Sotomayor, and Jorda´n (2008)

1 SA, SE, STR

EC

Imelouane et al. (2009)

1 BS, SA

EC

3 LM, SA

EC, PA, Sh

AN, PC

AN, FS, MM, RS

Va´gi, Sima´ndi, et al. (2005)

Hussain et al. (2008) Kaya, Yig˘it, and Benli (2008)

Mentha piperita

Melissa officinalis

Cuminum cyminum

Carum carvi

Foeniculum vulgare

Curcuma longa

Zingiber officinale

1 BC, LM, SA, SE

EC, KP, PA, PV, CA STm, YE

˙I¸scan, Kirimer, Ku¨rkcu¨og˘lu, Bas¸er, and Demirci (2002)

1 EF, SA

EC, KP, PA, STm, SeM

Hammer, Carson, and Riley (1999)

1 BS, MF, SL, SA, SE

EC, PA, SaE, ST, CA SS

4 BS, SA, SE

EC, PA

1 SA, StF

EC

Allahghadri et al. (2010)

1 LM, SA

EC

Gachkar et al. (2007)

1 BC, ML, SA

EC, PM, PT, SaE CA

Simic et al. (2008) AA, AF, AN, FTr, FSp, MM, PeF, PO

1 BC, BMe, BS, SA

EC, Ps, ST, SS

AA, FE

Begum, Bhuiyan, Chowdhury, Hoque, and Anwar (2008)

1 BS

EC

AN, FS, RS

Anwar et al. (2009)

1 BS, SA

EC, PA

AN

Shahat et al. (2011)

5 BS, SA

EC, PA, PM, ST

5 BC, CP, SA

CJ, EC, SaE

1 SA

KP, PV, PA

1 SA

CA

CA

CA

Mimica-Dukic et al. (2004) AN

Ertu¨rk (2006)

Srinivasan, Nathan, Suresh, and Perumalsamy (2001) CA

MM

Sunilson et al. (2009)

AF, AN, AO, AS, FM

Singh et al. (2008) Hammer et al. (1999) Continued

Table 3.2 Antimicrobial activity of selected medicinal plants—cont'd Antimicrobial activity Medicinal plant

-a Gþ bacteria

Ginkgo biloba

6 EF, SA, SE

Matricaria chamomilla 1 BC, EF, LI, SA

Eucalyptus radiata

G
bacteria

Yeast Fungi

Source

CA

Mazzanti et al. (2000)

EC, PM, SC, SD CA

A, AN

Abdoul-Latif et al. (2011)

1 BS, LM, MF, SA, SE EC, SaE, STm

Sokovic´, Glamocˇlija, Marin, Brkic´, and van Griensven (2010)

5 BS, SA

EC, KP, PA, PM, ST

Srinivasan et al. (2001)

1 SA

EC

Ghalem and Mohamed (2008)

a Antimicrobial activity of (1) essential oil, (2) supercritical fluid extract (SFE), (3) methanolic extract, (4) ethanolic extract, (5) water extract, and (6) ethyl acetate extract. AA, Alternaria alternata; A, Aspergillus sp.; AF, Aspergillus flavus; AO, Aspergillus oryzae; AN, Aspergillus niger; AS, Aspergillus solani; AV, Aspergillus variecolor; AT, Aspergillus terreus; BC, Bacillus cereus; BM, Bacillus macerans; BMe, Bacillus megaterium; BS, Bacillus subtilis; CJ, Campylobacter jejuni; CA, Candida albicans; CP, Clostridium perfringens; EF, Enterococcus faecalis; EC, Escherichia coli; FA, Fusarium acuminatum; FE, Fusarium equiseti; FG, Fusarium graminearum; FM, Fusarium moniliforme; FO, Fusarium oxysporum; FS, Fusarium solani; FSp, Fusarium sporotrichioides; FT, Fusarium tabacinum; FTr, Fusarium tricinctum; K, Klebsiella sp.; KO, Klebsiella oxytoca; KP, Klebsiella pneumoniae; LI, Listeria innocua; LM, Listeria monocytogenes; MF, Micrococcus flavus; ML, Micrococcus luteus; M, Mucor sp.; MM, Mucor mucedo; P, Penicillium sp.; PC, Penicillium cyclopium; PeF, Penicillium funiculosum; PeM, Penicillium madriti; PO, Penicillium ochrochloron; POx, Penicillium oxalicum; PP, Penicillium purpurogenum; PM, Proteus mirabilis; PV, Proteus vulgaris; Ps, Pseudomonas sp.; PA, Pseudomonas aeruginosa; PF, Pseudomonas fluorescens; PT, Pseudomonas tolaasii; R, Rhizopus sp.; RS, Rhizopus solani; RSt, Rhizopus stolonifer; Sml, Salmonella sp.; SC, Salmonella choleraesuis; SaE, Salmonella enteritidis; SPt, Salmonella paratyphi; ST, Salmonella typhi; STm, Salmonella typhimurium; SL, Sarcina lutea; S, Serratia sp.; SeM, Serratia marcescens; Sh, Shigella sp.; SD, Shigella dysenteriae; SF, Shigella flexneri; SS, Shigella sonnei; SA, Staphylococcus aureus; SE, Staphylococcus epidermidis; STR, Streptococcus sp.; StF, Streptococcus faecalis; SP, Streptococcus pyogenes; SM, Streptococcus mutans; YE, Yersinia enterocolitica.

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biologically active components of medicinal plants as chemopreventive agents seems to be very promising. There has been research into various anticancer effects of medicinal plants, through such mechanisms as increasing endogenous protective enzymes, protecting DNA from free radical-induced structural damage, encouraging the self-destruction of aberrant cells (apoptosis), and inhibiting tumor growth (Hedges & Lister, 2007). Because cancer is a multifactorial disease, there are many ways in which plant anticarcinogens are able to exert a protective effect. Phenolic compounds belong to constituents that may inhibit carcinogenesis by affecting the molecular events in the initiation, promotion, and progression stages. Flavonoids of the flavone, flavonol, flavanone, and isoflavone classes possess antiproliferative effects in different cancer cell lines including colon, prostate, leukemia, liver, stomach, cervix, pancreas, and breast cancer cell lines. The capability of flavonoids for growth inhibition and induction of apoptosis cannot be predicted on the basis of their chemical composition and structure (Kuntz, Wenzel, & Daniel, 1999). In addition, the bioavailability of the dietary polyphenols is discussed extensively because the tissue levels of the effective compounds determine the biological activity. Understanding the bioavailability and blood and tissue levels of polyphenols is also important in extrapolating results from studies in cell lines to animal models and humans (Yang, Landau, Huang, & Newmark, 2001). Generally, there is a lack of clinical research on the effects of medicinal plants on cancer in humans, though there are a number of in vitro and animal studies showing promising results. Similarly, most medicinal plants show varying degrees of antioxidant activity in vitro, but their precise effects in vivo have not been established yet. Several commonly used aromatic plants have been identified by the National Cancer Institute as possessing cancer-preventive properties. These plants include members of the Lamiaceae family, such as basil, mint, oregano, rosemary, sage, and thyme, plants of the Zingiberaceae family (turmeric and ginger), and some members of Apiaceae family (caraway, cumin, and fennel) (Caragay, 1992). Wang, Li, Luo, Zu, and Efferth (2012) investigated that essential oil of rosemary exhibited the strong cytotoxic activities toward human ovarian cancer cell lines and human hepatocellular liver carcinoma cell line. Essential oil had greater activity than its components (essential oil > a-pinene > b-pinene > 1,8-cineole). Some plants, such as sage and fennel, have been shown to stimulate the activity of endogenous protective enzymes, which have major antioxidant or detoxifying roles. Others, such

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as thyme, protect the structural integrity of DNA from free radical damage. Radical scavenging, metal chelating, and protecting lipids from peroxidation can also prevent steps in the cascade of events that lead to cancer (Hedges & Lister, 2007). Pretner et al. (2006) assessed that the treatment with standardized G. biloba extract (EGb 761) inhibited the proliferation of breast, glioma, and hepatocarcinoma cell lines. As they reported in vivo treatment with ginkgo extract led to dose-dependent decreases in breast cancer and glioma cell lines in nude mice. Ginkgo extract therefore could be useful in preventing or treating cancer invasiveness and metastasis. Very promising medicinal plant with anticancer activity is turmeric, derived from the rhizome of C. longa. Preclinical studies in a variety of cancer cell lines (breast, cervical, colon, gastric, hepatic, leukemia, oral epithelial, ovarian, pancreatic, and prostate) have consistently shown that curcumin possesses anticancer activity in vitro and in preclinical animal models. The robust activity of curcumin in colorectal cancer showed the safety and tolerability of curcumin in colorectal cancer patients. In vitro evidence and completed clinical trials suggested that curcumin may be useful for the chemoprevention of colon cancer in humans (Johnson & Mukhtar, 2007). Ramsewak, DeWitt, and Nair (2000) showed that curcumin I, curcumin II (monodemethoxycurcumin), and curcumin III (bisdemethoxycurcumin) possess activity against leukemia, colon, CNS, melanoma, renal, and breast cancer cell lines. The inhibition of COX-I (cyclooxygenase I) and COX-II enzymes by the curcumins was observed. Curcumins I–III were active against COX-I enzyme and showed 32–39.2% inhibition of the enzyme and also good inhibition of the COX-II enzyme with 58.9–89.7% inhibition.

6.3. Influences on cardiovascular diseases Cardiovascular diseases remain the world’s leading cause of death. The relative contributions of individual lipoproteins to overall cardiovascular risk have been intensively studied. The role of LDLs in causing atherosclerosis is well known. Oxidative modification of LDL is believed to play a crucial role in atherogenesis. Atherosclerosis is an inflammatory disorder that may be initiated by several factors such as mentioned LDLs. LDLs enter the artery wall from plasma. They may also return to the plasma. However, if the plasma level of LDLs exceeds a threshold, they enter the artery faster than they can be removed and thus accumulate. When they accumulate, they become modified, including being oxidized. Oxidized LDLs are a potent inducer of developing atherosclerotic plaque. High-density lipoproteins (HDLs) protect against the disease as they contain an enzyme, paraoxonase, which is believed to confer

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protection against oxidation of LDL cholesterol in the artery wall. One of a key anti-atherogenic mechanism of HDL cholesterol is the removal of excess lipids from the vascular wall by HDL cholesterol (Barter, 2005). Studies concerned with atherogenicity of oxidized oils and LOOH indicate that oxidized oils are more atherogenic than unheated oils and can therefore cause arterial and cardiac damage (Esterbauer, 1993). Atherosclerosis can thereby be slowed down or inhibited by preventing the oxidation of LDLs using a high daily intake of antioxidants. Protective role of carotenoids in cardiovascular disease is assumed due to the highly conjugated double bonds in their structure. It is supposed that carotenoids help prevent LDL oxidation and reduce oxidative stress at the plaque formation (Kohlmeier & Hastings, 1995). Epidemiological studies showed that also a high intake of vitamin E could reduce the risk of coronary heart diseases. And also, the protective effects of phenolic compounds, flavonoids against cardiovascular diseases were confirmed (Heim et al., 2002); Hertog, Feskens, Hollman, Katan, and Kromhout (1993); Hollman and Katan (1999). Therefore, the consumption of certain medicinal plants, containing antioxidants such as phenols, can reduce cardiovascular diseases incidence (Craig, 1999). Yamamoto, Yamada, Naemura, Yamashita, and Arai (2005) mentioned that medicinal plants such as thyme and rosemary showed significant antithrombotic activity in vitro and in vivo. The mechanism of their antithrombotic effect may involve a direct inhibitory effect on platelets. Neither herb affected flow-mediated vasodilation. Saghir, Sadiq, Nayak, and Tahir (2012) investigated that caraway aqueous seeds extract decreased lipid levels in diet-induced hyperlipidemic rats. Caraway (C. carvi) significantly decreased the levels of serum triglycerides, LDL, and total cholesterol in rats more effectively than the simvastatin. Caraway constituents, especially flavonoids and carvone with strong antioxidant activity, might be involved in hypolipidemia. Choi and Hwang (2004) showed that methanolic extracts of fennel (F. vulgare) increased the plasma superoxide dismutase and catalase activities and the HDL-cholesterol level in rats. Therefore, they suppose that fennel extracts may reduce the risk of inflammation-related diseases. Liebgott et al. (2000) evaluated that part of the cardioprotection afforded by G. biloba extract (EGb 761) is due to a specific action of its terpenoid constituents and that this effect involves a mechanism independent of direct free radical scavenging. Thus, the terpenoid constituents of ginkgo extract and the flavonoid metabolites that are formed after in vivo administration of the extract act in a complementary manner to protect against myocardial ischemia–reperfusion injury.

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6.4. Additional health effects Medicinal plants and their components possess a range of beneficial preventive properties. They show many promising effects for various health problems, such as colds, coughs, throat irritations, stomachache, indigestion, and gastrointestinal diseases, and have also positive protecting activities such as spasmolytic, sedative, antiviral, anti-inflammatory, antiseptic, hepatoprotective, antihyperglycemic, and immunostimulating. Because of the amounts of medicinal plants consumed are usually small, individual plants do not make a significant contribution to the diet. When used as remedies or drug constituents, the bioactive components of medicinal plants will be more concentrated. However, they are more efficient against health problems rather than in treating them. Moreover, many studies are mainly based on in vitro assays that do not necessarily reflect the human physiological mechanisms in vivo. Additional health effects of selected medicinal plants in various forms are presented in Table 3.3. Table 3.3 Additional health effects of selected medicinal plants Medicinal plant Type of extract Health effect Source

Rosmarinus Water officinalis Water

Hepatoprotective

Amin and Hamza (2005)

Diuretic

Haloui, Louedec, Michel, and Lyoussi (2000)

Essential oil

Antimycotoxigenic

Rasooli et al. (2008)

Chloroform

Anti-inflammatory

Altinier et al. (2007)

Ethanol

Antiulcerogenic

Dias, Foglio, Possenti, and de Carvalho (2000)

Ethanol

Antinociceptive

Gonza´lez-Trujano et al. (2007)

Essential oil

Antiproliferative

Hussain et al. (2010)

Ethanol

Antihyperglycemic

Bakırel, Bakırel, Keles¸, ¨ lgen, and Yardibi U (2008)

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Table 3.3 Additional health effects of selected medicinal plants—cont'd Medicinal plant Type of extract Health effect Source

Salvia officinalis

Origanum vulgare

Origanum majorana

Thymus vulgaris

Ocimum basilicum

Water

Hepatoprotective

Amin and Hamza (2005)

Alcohol

Treatment for Alzheimer’s disease

Akhondzadeh et al. (2003a)

Ethanol

Memory retention

Eidi, Eidi, and Bahar (2006)

Ethanol

Anti-inflammatory

Yoshino, Higashi, and Koga (2006)

Water

Antihyperglycemic

Lemhadri, Zeggwagh, Maghrani, Jouad, and Eddouks (2004)

Essential oil

Cytotoxic

Hussain et al. (2011)

Methanol

Antimutagenic

¨ zbek et al. (2008) O

Ethanol

Antiproliferative

Abdel-Massih, Fares, Bazzi, El-Chami, and Baydoun (2010)

Essential oil

Improve the health of Mohamed, Saad, and patients with asthma Khalek (2008)

Anticonvulsant Pet ether, chloroform, acetone, methanol, water

Deshmane, Gadgoli, and Halade (2007)

Essential oil

Cytotoxic

Hussain et al. (2011)

Essential oil

Antiaflatoxigenic

Razzaghi-Abyaneh et al. (2009)

Water

Relaxant

Boskabady, Aslani, and Kiani (2006)

Ethanol

Antimalarial

Singh, Raj, et al. (2010)

Ethanol

Hepatoprotective

Meera, Devi, Kameswari, Madhumitha, and Merlin (2009) Continued

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Table 3.3 Additional health effects of selected medicinal plants—cont'd Medicinal plant Type of extract Health effect Source

Mentha piperita

Melissa officinalis

Cuminum cyminum

Water

Antiallergic

Inoue, Sugimoto, Masuda, and Kamei (2002)

Menthol

Analgesic

Galeotti, Mannelli, Mazzanti, Bartolini, and Ghelardini (2002)

Essential oil

Immunomodulatory

Cosentino et al. (2009)

Essential oil

Reduction of irritable Grigoleit and Grigoleit bowel syndrome (2005)

Volatile oil

Antiviral

Allahverdiyev, Duran, Ozguven, and Koltas (2004)

Essential oil

Relaxant

Sadraei, Ghannadi, and Malekshahi (2003)

Methanol

Neuroprotective

Lo´pez et al. (2009)

Essential oil

Antidiabetic

Chung, Cho, Bhuiyan, Kim, and Lee (2010)

Ethanol, water

Antiproliferative

Encalada et al. (2011)

Water

Anti-inflammatory

Water

Antinociceptive

Birdane, Bu¨yu¨kokurog˘lu, Birdane, Cemek, and Yavuz (2007)

Methanol

Anticonvulsant

Hariry (2011)

Ethanol

Anxiolytic

Taiwo et al. (2012)

Ethanol

Antidepressant-like

Alcohol

Treatment for Alzheimer’s disease

Akhondzadeh et al. (2003b)

Volatile oil

Cytotoxic

Allahghadri et al. (2010)

Water

Hypolipidemic

Dhandapani, Subramanian, Rajagopal, and Namasivayam (2002)

Plant (in vivo)

Chemopreventive

Gagandeep, Dhanalakshmi, Me´ndiz, Rao, and Kale (2003)

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Table 3.3 Additional health effects of selected medicinal plants—cont'd Medicinal plant Type of extract Health effect Source

Essential oil

Anticonvulsant

Sayyah, Mahboubi, and Kamalinejad (2002)

Essential oil

Antinociceptive

Sayyah, Peirovi, and Kamalinejad (2002)

Water

Relaxant

Boskabady, Kiani, and Azizi (2005)

Water

Antitussive

Boskabady, Kiani, Azizi and Khatami (2006)

Benzene

Antitumor

Mekawey, Mokhtar, and Farrag (2009)

Plant (in vivo)

Antidiabetic

Willatgamuwa, Platel, Saraswathi, and Srinivasan (1998)

Carum carvi Water

Diuretic

Lahlou, Tahraoui, Israili, and Lyoussi (2007)

Foeniculum Methanol vulgare Methanol

Anti-inflammatory

Choi and Hwang (2004)

Curcuma longa

Analgesic

Water

Antihypertensive

Bardai, Lyoussi, Wibo, and Morel (2001)

Essential oil

Hepatoprotective

¨ zbek et al. (2003) O

Essential oil

Antithrombotic

Tognolini et al. (2007)

Water

Oculohypotensive

Agarwal, Gupta, Agrawal, Srivastava, and Saxena (2008)

Ethanol, essential oil

Relaxant

Boskabady and Khatami (2003)

Water

Antimutagenic

Ebeed et al. (2010)

Water

Chemopreventive

Curcumins

Cytotoxic

Curcumins

Anti-inflammatory

Ramsewak et al. (2000)

Continued

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Table 3.3 Additional health effects of selected medicinal plants—cont'd Medicinal plant Type of extract Health effect Source

Curcuma longa

Zingiber officinale

Curcumin

Hypolipidemic

Babu and Srinivasan (1997)

Curcumin

Neuroprotective

Rajakrishnan, Viswanathan, Rajasekharan, and Menon (1999)

Water

Antidepressant

Yu, Kong, and Chen (2002)

Ethanol

Antischistosomal

EL-Ansary, Ahmed, and Aly (2007)

Crude proteins

Hemagglutinating

Sangvanich et al. (2007)

Methanol

Hypotensive

Adaramoye et al. (2009)

Methanol

Vasorelaxant

Water

Antiviral

Kim et al. (2009)

Ethanol

Hypoglycemic

Kuroda et al. (2005)

Curcumin

Radioprotective

Inano and Onoda (2002)

Ethanol

Analgesic

Ojewole (2006)

Ethanol

Anti-inflammatory

Ethanol

Hypoglycemic

Ethanol

Antiproliferative

Water

Hypocholesterolemic Unnikrishnan, Indu, and Ozarkar (2009)

Water

Antidiabetic

Water

Hypolipidemic

Ethanol

Anticataract

Kumar, Singh, Ali, and Tyagi (2011)

Water

Antithrombotic

Thomson et al. (2002)

Water

Gastroprotective

Nanjundaiah, Annaiah, and Dharmesh (2011)

Ethanol

Radioprotective

Haksar et al. (2006)

Harliansyah, Murad, Ngah, and Yusof (2007)

Al-Amin, Thomson, Al-Qattan, PeltonenShalaby, and Ali (2006)

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Table 3.3 Additional health effects of selected medicinal plants—cont'd Medicinal plant Type of extract Health effect Source

Ginkgo biloba

Ethanol

Chemopreventive

Yusof, Ahmad, Das, Sulaiman, and Murad (2009)

Water

Antidiarrhoeal

Daswani, Brijesh, Tetali, Antia, and Birdi (2010)

Commercial (EGb 761)

Treatment for Mazza, Capuano, Bria, Alzheimer’s dementia and Mazza (2006)

Commercial (Ph-Gb)

Neuroprotective

Calapai et al. (2000)

Commercial

Hepatoprotective

Shenoy, Somayaji, and Bairy (2001)

Commercial (EGb 761)

Cardioprotective

Liebgott et al. (2000)

Commercial

Antistress

Rai, Bhatia, Sen, and Palit (2003)

Ethanol

Vasodilating

Nishida and Satoh (2004)

Commercial (EGb 761)

Anticlastogenic

Emerit et al. (1995)

Commercial (EGb 761)

Neuroprotective in Parkinson’s disease

Kim, Lee, Lee, and Kim (2004)

Commercial

Treatment for Raynaud’s disease

Muir, Robb, McLaren, Daly, and Belch (2002)

Commercial

Treatment for glaucoma

Ritch (2000)

Commercial

Anti-inflammatory

Abdel-Salam, Baiuomy, El-batran, and Arbid (2004)

Analgesic

Abdel-Salam et al. (2004)

Antihyperglycemic

Cemek, Kag˘a, S¸ims¸ek, Bu¨yu¨kokuroglu, and Konuk (2008)

Gastroprotective

Cemek, Yilmaz, and Bu¨yu¨kokurog˘lu (2010)

Matricaria Ethanol chamomilla Ethanol

Continued

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Table 3.3 Additional health effects of selected medicinal plants—cont'd Medicinal plant Type of extract Health effect Source

Ethanol

Immunomodulatory

Amirghofran, Azadbakht, and Karimi (2000)

Water, methanol

Antiproliferative

Srivastava and Gupta (2007)

Water

Kato et al. (2008) Prevention of hyperglycemia and diabetic complications

Water

Anti-inflammatory

Srivastava, Pandey, and Gupta (2009)

Water

Antiulcer

Rezq and Elmallh (2010)

7. CONCLUSION Aromatic plants have been extensively studied due to their antioxidant and antimicrobial effects and other positive health benefits such as prevention of cardiovascular diseases, atherosclerosis, inflammation, or reducing the risk of cancer. To commonly used medicinal plants with antioxidantactivity belong plants from several families, especially Lamiaceae (rosemary, sage, oregano, marjoram, basil, thyme, mints, balm), Apiaceae (cumin, fennel, caraway), and Zingiberaceae (turmeric, ginger). The antioxidant properties of medicinal plants depend on the plant and its characteristics such as growing conditions and processing, further concentration and composition of present antioxidants (phenolic compounds such as phenolic acids, flavonoids, terpenes, carotenoids, and vitamins). In addition, extraction technique and determination method of antioxidant capacity are important for evaluation of medicinal plants quality.

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