Valorisation of Mangifera indica crop biomass residues

Industrial Crops & Products 124 (2018) 284–293

Contents lists available at ScienceDirect

Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop

Valorisation of Mangifera indica crop biomass residues a

b

a

T b

Didier G. Mouho , Andreia P. Oliveira , Charles Guillaume Kodjo , Patrícia Valentão , ⁎ Zana Adama Ouattaraa, Yves-Alain Bekroa, Paula B. Andradeb, a

Laboratoire de Chimie Bio-Organique et de Substances Naturelles (LCBONS), UFR-SFA, Université Nangui Abrogoua, 02 B.P. 801 Abidjan 02, Cote d’Ivoire1 REQUIMTE/LAQV, Laboratório de Farmacognosia, Departamento de Química, Faculdade de Farmácia, Universidade do Porto, R. Jorge Viterbo Ferreira, nº 228, 4050313 Porto, Portugal b

A R T I C LE I N FO

A B S T R A C T

Keywords: Mangifera indica L. Metabolic profiling Antioxidant Antidiabetic Cytotoxic

Mangifera indica L. is one of the most important commercial plants worldwide in terms of production, marketing and consumption. Although the fruit is widely studied, few works focus other vegetal materials, which could be excellent sources of metabolites with potential application in several industries. Additionally, some M. indica varieties remain unstudied. The aim of this work was to explore for the first time the chemical composition and the biological properties of aqueous extracts from M. indica var. Nunkourouni leaf and stem bark. Malic and quinic acids were the most abundant organic acids. Mangiferin and gallic acid were the main phenolics in stem bark and leaves, respectively. A concentration-dependent activity was noticed against several reactive species, stem bark displaying stronger antioxidant capacity. The two materials also inhibit α-glucosidase and α-amylase, leaves being more potent. The cytotoxic effects on AGS cells were also approached, leaves being the most active material. The results suggest that M. indica leaf and stem bark could be valuable sources of bioactive compounds, contributing to the valorisation of these materials and their further application in high prevalence diseases.

1. Introduction The genus Mangifera belongs to the Anacardiaceae family, order Sapindales, comprising 73 genera and about 850 species (Tharanathan et al., 2006). Mangifera indica L., commonly known as mango, is a long living large evergreen tree native from tropical Asia, being now found naturalized in many tropical and sub-tropical regions (Wauthoz et al., 2007). Actually, this tree is cultivated on an area of approximately 3.7 million ha worldwide and its fruit is one of the most important fruit crops, having socio-economic significance in many countries (Tharanathan et al., 2006; Jahurul et al., 2015). In West Africa mango varieties are grouped into four categories: the local or polyembryonic mangos (Nunkourouni and Number One), which are used as graft support for producing non-fibrous fruits intended for marketing; the first monoembryonic varieties propagated by grafting (Amélie, Julie, Sabot, Djibelor and Cuisse Madame); the Floridian varieties, also monoembryonic and propagated by grafting, introduced later and used for export (Kent, Keitt, Palmer, Zill, Valencia, Smith, Irwin and Haden); varieties used for the regional markets (Brooks, Davis-Haden, Miami Late, Springfels, Beverly, Eldon and Ruby) (Rey et al., 2004). Nunkourouni variety, also known as Tête de Chat, is widespread throughout

West and Central Africa. Nevertheless, to our knowledge, there is no previous study involving this M. indica variety. Besides the use of the fruit for human consumption, mango leaf and stem bark are known to possess several biological properties, including antioxidant, anti-inflammatory and antidiabetic ones (Sanchez et al., 2000; Aderibigbe et al., 2001; Garrido et al., 2004). Actually, the use of mango-derived extracts as herbal drugs is widespread in traditional medicine. For example, mango seeds are used in India as an antidiarrheal agent (Sairam et al., 2003). Fresh mango kernel is consumed in Fiji to treat dysentery and asthma (Singh, 1986). Leaves have been widely used in tropical Africa in infusions due to their antipyretic and antidiarrheal effects, and the stem bark is used to prepare an antihypertensive, antidiarrheal and an antiulcer infusion (Wong, 1976; Lauricella et al., 2017). Several studies have focused on mango fruit, its by-products (peels and seeds) and stem bark, describing the presence of high levels of health-promoting substances, such as phenolic compounds, carotenoids, tocopherols and sterols (Núñez Sellés et al., 2002; Barreto et al., 2008; Masibo and He, 2008; Kim et al., 2010; Jahurul et al., 2015). Concerning to M. indica leaf, there are some works reporting its physicochemical parameters (Romero et al., 2015), its potential to

⁎

Corresponding author. E-mail address: pandrade@ff.up.pt (P.B. Andrade). 1 www.lablcbosn.com. https://doi.org/10.1016/j.indcrop.2018.07.028 Received 19 December 2017; Received in revised form 7 June 2018; Accepted 11 July 2018 0926-6690/ © 2018 Elsevier B.V. All rights reserved.

Industrial Crops & Products 124 (2018) 284–293

D.G. Mouho et al.

Abrogoua (Ivory Coast). In order to obtain a representative sample, leaves and stem bark were collected from different trees. Samples were collected to sterile plastic bags and immediately transported to the laboratory in insulated sealed ice-boxes wash under running water and dehydrated at 20 °C for 20 days, protected from light. The plant material was then powdered (mean particle size lower than 910 μm). Voucher specimens were deposited at Department of Pharmacognosy, Faculty of Pharmacy, Porto University (MIL072016 and MISB072016).

scavenge heavy metal pollutants (Laskara et al., 2017) and different techniques to extract its compounds (Kulkarni and Rathod, 2014). Recently, Pan et al. (2018) isolated and identified twenty-two phenolic compounds (5 benzophenones and 17 flavonoids) from the different fractions of mango leaves. Nonetheless, it is widely known that the cultivar, the plant physiological stage and the climatic conditions are parameters that influence the phenolic composition (Scalbert and Williamson, 2000). Since agricultural industry produces billions of tons of residues in non-edible portions derived from the cultivation and processing of a particular crop, including primary biomass residues (leaves, roots, stems), that cause pollution, management and economic problems (Santana-Méridas et al., 2012), several studies have been developed to use the agricultural residues as a source of high-value products (Figueiredo-González et al., 2017; Zeković et al., 2017). Thus, the main goal of this work was to expand the knowledge on mango leaves and stem bark, valuing the potential application of these residues in the treatment of diseases with high prevalence worldwide. To achieve these purposes, phenolic compounds and organic acids profiles of aqueous extracts from leaves and stem bark of mango from var. Nunkourouni were characterized, for the first time, by high pressure liquid chromatography coupled to a diode-array detector (HPLC-DAD) and high pressure liquid chromatography coupled to an ultraviolet detector (HPLC-UV), respectively, both analytical methods being fully validated. Antioxidant potential, checked against 2,2-diphenyl-1-picrylhydrazyl (DPPH%), superoxide anion (O2%−) and nitric oxide (%NO) radicals, and lipid peroxidation, was assessed through spectrophotometric assays. Antidiabetic capacity, concerning to α-glucosidase and α-amylase inhibitory capacity, was evaluated by spectrophotometric microassays. The cytotoxic potential of both herbal infusions against human gastric cancer cells (AGS) was approached.

2.3. Extraction In order to simulate the usual form of human consumption (Wong, 1976), an aqueous extract of each material was prepared by boiling ca. 5 g of powdered material for 30 min, in 500 mL of distilled water. The resulting extracts were filtered using a Büchner funnel and then freezedried in a Virtis SP Scientific Sentry 2.0 apparatus (Gardiner, NY 12525, USA). The lyophilized extracts were kept in a desiccator in the dark until analysis. The extraction yields of the aqueous extract from leaves and stem bark were 28.72% and 26.48%, respectively.

2.4. HPLC-DAD for phenolic compounds analysis Each lyophilized extract was redissolved in water, filtered and 20 μL were analysed on an analytical HPLC unit (Gilson), using a Spherisorb ODS2 (25.0 × 0.46 cm; 5 μm, particle size) column, according to a described procedure (Oliveira et al., 2009). The solvent system used was a gradient of water-formic acid (19:1) (A) and methanol (B), starting with 5% methanol and installing a gradient to obtain 15% B at 3 min, 25% B at 13 min, 30% B at 25 min, 35% B at 35 min, 45% B at 39 min, 45% B at 42 min, 50% B at 44 min, 55% B at 47 min, 70% B at 50 min, 75% B at 56 min and 80% B at 60 min, at a solvent flow rate of 0.9 mL/min. Detection was achieved with a Gilson Diode Array Detector (DAD). Spectral data from all peaks were accumulated in the range 200–400 nm, and chromatograms were recorded at 255, 280, 320 and 350 nm. The data were processed on a Clarity Software system. Peak purity was checked by the software contrast facilities. The compounds in each extract were identified by comparing their retention times and UV–vis spectra in the 200–400 nm range with authentic standards, and their quantification was achieved by the absorbance recorded in the chromatograms relative to external standards. Ellagic acid and quercetin-3-O-glucoside were determined at 255 and 350 nm, respectively. Gallic acid derivative was determined as gallic acid at 280 nm, and mangiferin derivative as mangiferin at 320 nm. Each extract was analysed in triplicate.

2. Materials and methods 2.1. Standards and reagents Oxalic, aconitic, citric, ascorbic, tartaric, malic, quinic, shikimic, fumaric, gallic and linoleic acids were from Sigma-Aldrich (St. Louis, MO, USA); ellagic acid, mangiferin and quercetin-3-O-glucoside were from Extrasynthèse (Genay, France). Sodium nitroprusside dihydrate was from Riedel-de Haën (St. Louis, MO). N-(1-Naphthyl)ethylenediamine dihydrochloride, phosphoric acid, iron (II) sulphate (FeSO4·7H2O) and methanol were from Merck (Darmstadt, Germany). Sulphanilamide, β-nicotinamide adenine dinucleotide (NADH), nitroblue tetrazolium chloride (NBT), phenazine methosulphate (PMS), DPPH, acarbose, α-glucosidase (from Saccharomyces cerevisiae), αamylase (from porcine pancreas), 4-nitrophenyl-α-D-glucopyranoside (PNP-G), dinitrosalicylic acid, soluble starch and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) were obtained from Sigma-Aldrich. Ethanol and diethyl ether were from Panreac (Barcelona, Spain) and Fisher Scientific (Loughborough, UK), respectively. The water was treated in a Milli-Q water purification system (Millipore, Bedford, MA, USA). The Chromabond C18 SPE columns (70 mL/10,000 mg) were purchased from Macherey-Nagel (Duren, Germany). Dulbecco’s Modified Eagle Medium (DMEM), Dulbecco’s phosphate buffered saline, heat inactivated foetal bovine serum (FBS), Pen Strep solution (penicillin 5000 units/mL and streptomycin 5000 μg/mL) and 0.25% trypsin-EDTA (1X) were purchased from Gibco, InvitrogenTM (Grand Island, NY, USA).

2.5. HPLC-UV for organic acids analysis Before HPLC analysis, each lyophilized extract was dissolved in acid water (pH 2 with HCl). The solution obtained was passed through a SPE C18 column, previously conditioned with 30 mL of methanol and 70 mL of acid water. The aqueous solution was then evaporated to dryness under reduced pressure (40 °C), redissolved in sulphuric acid 0.01 N (1 mL) and 20 μL were analysed on an analytical HPLC unit (Gilson), using an ion exclusion column Nucleogel® Ion 300 OA (300 × 7.7 mm), in conjunction with a column heating device set at 30 °C, according to a described procedure (Oliveira et al., 2009). Elution was carried out at a solvent flow rate of 0.2 mL/min, isocratically, with sulphuric acid 0.01 N as the mobile phase. Detection was performed with a Gilson UV detector set at 214 nm. The data were processed on a Clarity Software system (Data Apex, Prague, Czech Republic). Organic acids quantification was achieved by the absorbance recorded in the chromatograms relative to external standards.

2.2. Plant material The young leaves of M. indica and stem bark were collected in Bondoukou (North East of Ivory Coast), in July 2016. Plant material was botanically identified by Dr. Vangha Madeleine from the Laboratory of Physiology and Botanical of University of Nangui 285

Industrial Crops & Products 124 (2018) 284–293

D.G. Mouho et al.

Table 1 Validation parameters of organic acids and phenolic compounds analyses methods. Metabolites Organic acids Oxalic Aconitic Citric Tartaric Malic Quinic Shikimic Fumaric Phenolics Gallic acid Mangiferin Quercetin-3-O-glucoside Ellagic acid a b c

Regression equation

R2

LODa (μg/mL)

LOQb (μg/mL)

Repeatability (CV%)c

Inter-day Precision (CV%)

Recovery (%)

y = 3752.5x – 65.197 y = 15208x + 74.300 y = 589.6x – 60.494 y = 1111.7x – 26.489 y = 363.23x + 22.742 y = 486.31x – 163.34 y = 26396x + 83.580 y = 12111x – 62.822

0.9910 0.9892 0.9972 0.9997 0.9980 0.9934 0.9973 0.9903

18.1 3.9 8.0 21.5 157.3 5.1 4.8 2.8

54.8 11.7 24.3 65.2 476.7 15.6 14.6 8.4

4.7 6.1 5.3 8.7 5.5 1.4 4.0 6.0

6.5 8.6 9.0 9.2 6.3 5.1 6.3 7.6

87.9 82.8 92.9 81.0 95.7 86.2 97.9 80.7

y = 74768x + 824.89 y = 52551x – 347.37 y = 60845x – 599.98 y = 164017x + 931.28

0.9992 0.9990 0.9993 0.9924

0.8 0.6 0.4 0.3

2.3 1.8 1.3 0.9

3.8 1.1 3.2 1.7

5.0 4.7 4.1 2.9

97.1 89.8 92.6 96.4

LOD, limit of detection. LOQ, limit of quantification. CV, coefficient of variation.

performed in triplicate. Results were compared with that of quercetin3-O-rutinoside (positive control), tested under the same conditions.

2.6. Methods validation 2.6.1. Linearity The linearity range of both analytical methods was assessed by building calibration curves using five different concentration levels of the phenolic compounds and organic acids, according to the range of concentrations found in the aqueous extracts from M. indica leaves and stem bark (Table 1).

2.7.3. Superoxide anion radical scavenging activity Superoxide anion radicals were generated by a NADH/PMS system according to a described procedure (Oliveira et al., 2009). The absorbance was read at 560 nm in the plate reader used for the other two reactive species. Three experiments were performed in triplicate. Results were compared with that of quercetin-3-O-rutinoside (positive control), tested under the same conditions.

2.6.2. Limits of detection and of quantification The limits of detection (LOD = 3.3*S0/b) and of quantification (LOQ = 10*S0/b) (where S0 is the standard deviation of signal-to-noise ratio of a low concentration standard and b is the slope of the calibration plot) for the analysed compounds were determined from calibration curve data (Table 1).

2.7.4. Lipid peroxidation inhibition assay The evaluation of the effect on the peroxidation of fatty acyl groups followed the methodology previously described by Ferreres et al. (2012). The absorbance was determined in a Helios α (Unicam) spectrophotometer, at 233 nm. Three experiments were performed in triplicate. Results were compared with that of quercetin (positive control), tested under the same conditions.

2.6.3. Repeatability and inter-day precision Repeatability was checked by analysing five times the same sample, by the same analyst, within the same day, and the inter-day precision was determined by analysing the same sample on five different days (three injections a day) (Table 1).

2.8. Antidiabetic activity 2.8.1. α-Glucosidase inhibitory activity The evaluation of the ability to inhibit α-glucosidase was determined spectrophotometrically in a Multiscan GO (Thermo Scientific, Finland) equipped with Skanlt 4.1 software, based on the reaction with 4-nitrophenyl α-D-glucopyranoside (Figueiredo-González et al., 2016). The absorbance was measured at 400 nm and three independent assays were performed in triplicate. Results were compared with that of acarbose (positive control), tested under the same conditions.

2.6.4. Recoveries In order to evaluate the recoveries, aliquots of known quantities of each organic acid and phenolic compound were treated as the aqueous lyophilized extracts and quantified by HPLC-UV and HPLC-DAD, respectively (Table 1). 2.7. Antioxidant activity 2.7.1. DPPH% scavenging activity The capacity to scavenge DPPH radical was determined spectrophotometrically in a 96-well plate reader (Multiskan GO, Thermo Scientific, Finland), by monitoring the disappearance of DPPH at 515 nm, according to a described procedure (Oliveira et al., 2009). The plate was incubated in the dark for 30 min at room temperature after the addition of DPPH%. Three experiments were performed in triplicate. Results were compared with that of quercetin-3-O-rutinoside (positive control), tested under the same conditions.

2.8.2. α-Amylase inhibitory activity The capacity to inhibit α-amylase was evaluated according to a described procedure (Figueiredo-González et al., 2016). The absorbance was read at 540 nm in a Helios α (Unicam) spectrophotometer (Thermo Scientific) and three independent assays were performed in triplicate. Results were compared with that of acarbose (positive control), tested under the same conditions.

2.7.2. Nitric oxide scavenging activity The potential of the aqueous extracts from stem bark and leaves of both species to scavenge %NO was assessed spectrophotometrically, at 562 nm, in the plate reader referred above for DPPH%, according to a described procedure (Oliveira et al., 2009). Three experiments were

2.9.1. Cell culture Human gastric adenocarcinoma cells line (AGS) from the American Type Culture Collection (LGC Standards S.L.U., Spain) were grown in DMEM supplemented with 10% FBS and 1% penicillin/streptomycin, and incubated at 37 °C, in a humidified atmosphere of 5% CO2. When

2.9. Cellular assays

286

Industrial Crops & Products 124 (2018) 284–293

D.G. Mouho et al.

cells reached 80–85% of confluence they were washed, trypsinized and subcultured in 96-wells plates at a density of 15.000 cells/well. 2.9.2. Cell viability To assess the effect of both aqueous extracts on AGS cells, the viability was assessed 24 h after extracts exposure, by the MTT reduction assay, according to a described procedure (Pereira et al., 2017). For this, MTT (final concentration 0.5 mg/ml) was added to each well and the plate was incubated for 90 min at 37 °C. The formazan was dissolved by addition of a DMSO/isopropanol mixture (3:1) and quantified spectrophotometrically at 560 nm. Results correspond to the mean of four independent experiments performed in triplicate, and are expressed as percentage of treated cells vs. control cells (cells without extract). Fig. 1. HPLC-UV organic acid profile of aqueous extracts from M. indica var. Nunkourouni stem bark. Detection at 214 nm. MP, mobile phase. Compounds´ identity as in Table 2.

2.9.3. Membrane integrity assay The effect of both aqueous extracts on membrane integrity was assessed by measuring the release of cytosolic lactate dehydrogenase (LDH) into the media, 24 h after extracts exposure, according to a previously described procedure (Pereira et al., 2017). LDH was determined in a microplate reader (Multiscan GO, Thermo Scientific, Finland) by measuring changes in absorbance at 340 nm due to NADH oxidation during the conversion of pyruvate to lactate. All the results correspond to the fold-increase of absorbance in treated vs control cells (cells without extract) of four independent experiments performed in triplicate.

Table 2 Organic acids and phenolics composition of the aqueous lyophilized extracts of M. indica var. Nunkourouni leaves and stem bark (mg/g dry lyophilized extract).a Compound Organic acid 1 Oxalic 2 Aconitic 3 Citric 4 Tartaric 5 Malic 6 Quinic 7 Shikimic 8 Fumaric Σ Phenolics 9 Gallic acid 10 Mangiferin 11 Mangiferin derivative 12 Quercetin-3-O-glucoside 13 Gallic acid derivative 14 Ellagic acid Σ

2.10. Statistical analysis Statistical analysis was performed using Graph Pad Prism 6 Software (San Diego, CA, USA). Since data displayed normality of distribution and homogeneity of variance, the analysis of variance t-test (unpaired t-test with Welch’s correction) was used to compare the existence of significant differences relatively to control. In all cases, p values lower than 0.05 were considered statistically significant. 3. Results and discussion 3.1. Methods validation The analytical methods used to determine both organic acids and phenolic compounds showed good linearity, with R2 values higher than 0.9892 for all studied metabolites. Regarding organic acids, LOD and LOQ values ranged from 2.80 to 157.3 μg/mL and from 8.4 to 476.7 μg/ mL, respectively (Table 1). In what concerns to phenolic compounds, LOD and LOQ values varied from 0.3 to 0.8 μg/mL and 0.9 to 2.3 μg/ mL, respectively (Table 1). Thus, we can conclude that both methods are sensitive (Table 1). In addition, the accuracy of the two analytical procedures was checked by recovery tests and values higher than 80.7% were found for all determined compounds, which can be considered satisfactory (Table 1). The coefficients of variation lower than 10% for repeatability and inter-day precision point out the high precision of the chromatographic systems and extraction procedures (Table 1). Overall, it can be concluded that these methods are reliable tools for the analysis of organic acids and phenolic compounds in these plant materials.

Leaves

Stem bark

20.8 ± 0.6*** 0.9 ± 0.2*,b 27.5 ± 2.1* 6.1 ± 0.9 46.4 ± 4.2** 28.8 ± 1.6* 0.3 ± 0.1*** 2.1 ± 0.1 132.9 ± 8.4*

5.1 ± 0.1 0.3 ± 0.1b 41.5 ± 3.9 4.1 ± 0.9 76.2 ± 2.5 46.4 ± 4.9 1.9 ± 0.1 1.7 ± 0.2 177.2 ± 5.6

66.7 ± 0.3*** 28.0 ± 2.1** nd 6.7 ± 0.3 6.9 ± 0.1 14.0 ± 0.5*** 122.3 ± 1.6**

1.2 ± 0.1 190.2 ± 13.2 35.9 ± 2.3 nd nd 3.9 ± 0.1 231.2 ± 15.6

a Values are expressed as mean ± standard deviation of three determinations; ∑, sum of the determined compounds; nd, not detected. b cis-Aconitic (2a) and trans-aconitic (2b) were quantified together as aconitic acid. * p < 0.05. ** p < 0.01. *** p < 0.001, comparing aqueous extracts of leaves and stem bark.

35% and 43% of the total organic acids content in aqueous extracts from leaves and stem bark, respectively (Table 2). Studies concerning to the organic acid composition of M. indica are scarce. Nevertheless, malic and citric acids were already described as the main organic acids in the fruits from four mango cultivars (Liu et al., 2013). Unlike what happens with stem bark, leaves possess considerable amounts of oxalic acid, which corresponds to ca. 16% of total organic acids content (Table 2). Oxalic and fumaric acids were reported in mango fruits as the minor components (Liu et al., 2013).

3.2. Organic acids 3.3. Phenolic compounds The characterization of the organic acids profile of M. indica leaves and stem bark by HPLC-UV revealed the presence of nine compounds (Fig. 1 and Table 2). As far as we are aware, aconitic, tartaric, quinic and shikimic acids are described for the first time in this species. The two plant materials have a similar qualitative profile; however, quantitative differences were found, stem bark being the richest one (Table 2). Malic acid was clearly the main compound, representing ca.

In what concerns to the phenolic composition, qualitative and quantitative differences were observed between the two M. indica materials (Fig. 2 and Table 2). Unlike mango fruits, in which several quercetin and kaempferol derivatives were identified (Ribeiro et al., 2008), the leaves are described to present a smaller diversity of flavonoids (Barreto et al., 2008), which is in agreement with our results. In 287

Industrial Crops & Products 124 (2018) 284–293

D.G. Mouho et al.

Fig. 2. HPLC phenolic profile of aqueous extracts from M. indica var. Nunkourouni leaves (A) and stem bark (B). Detection at 280 nm. Compounds’ identity as in Table 2.

Excepting for mangiferin, all the other determined phenolics are found in higher amounts in the aqueous extract from leaves (Table 2). This suggests that the high phenolic content of aqueous extract from stem bark is related with higher amounts of mangiferin, (ca. 82% of total phenolic content) (Table 2), in agreement with the results obtained by Sanchez et al. (2000). In addition, Saleh and El-Ansari (1975) also showed that the content of this xanthone was higher in stem bark than in leaves, as verified in our samples (Table 2). Gallic acid was clearly the main compound in the aqueous extract of the leaves, corresponding to ca. 54% of total phenolic content (Table 2), in contrast with that described by Barreto et al. (2008) and Pan et al. (2018). According to those works, mangiferin was the main metabolite in leaves from other mango cultivars (Barreto et al., 2008; Pan et al., 2018).

the leaves analysed herein only quercetin-3-O-glucoside was detected (Table 2 and Fig. 2), in opposition to that found for other cultivars, for which more than one quercetin derivative was described (Barreto et al., 2008; Pan et al., 2018). Nevertheless, it is well known that the phenolic composition varies as a function of the cultivar, the environmental conditions (including temperature, humidity and UV irradiation) at the site of collection and the growing stage (Ksouri et al., 2007). Concerning to the stem bark, no quercetin derivative was detected (Table 2), which agrees with the results obtained by Barreto et al. (2008). In quantitative terms, the aqueous extract from the stem bark presented higher amounts of these compounds (Table 2). Barreto et al. (2008) compared different tissues (peels, kernels, bark, old and young leaves) of seventeen mango cultivars and, for five of them, they found that young leaves had lower phenolic content than the bark. For example, the total phenolic content of the bark from Embrapa-142-alfa cultivar was about twice that of the young leaves (Barreto et al., 2008), which is in accordance with our results (Table 2). Thus, although it would be expected to find higher phenolic content in the leaves, as these metabolites act as UV filters, protecting some cell structures, like chloroplasts, from harmful effects of UV radiation (Treutter, 2006), the lower phenolic contents found in our leaves when compared to the bark could be related with the variety.

3.4. Antioxidant activity In the last decades, it has been demonstrated that oxidative stress is closely related with the development of certain diseases, such as diabetes, neurodegenerative disorders and cancer (Valko et al., 2006). Exhaustive investigation has been carried out to characterize the antioxidant properties of extracts from plant materials, once they constitute its common form of utilization in medicine and in food technology (Kintzios et al., 2010). So, the antioxidant potential of the aqueous 288

Industrial Crops & Products 124 (2018) 284–293

D.G. Mouho et al.

Fig. 3. Effects of M. indica var. Nunkourouni leaves and stem bark aqueous extracts against: (A) DPPH, (B) nitric oxide and, (C) superoxide anion radicals. Values show mean ± SD from three experiments performed in triplicate.

3.5. Antidiabetic activity

extracts from M. indica leaves and stem bark was checked against DPPH %, O2%−, %NO, and lipid peroxidation. A concentration-dependent pattern was observed in all assays. M. indica stem bark was the vegetal material with the strongest scavenging capacity, presenting IC50 values of 13.90 ± 0.70, 18.00 ± 2.21 and 99.00 ± 14.53 μg extract/mL against DPPH%, O2%− and %NO, respectively (Fig. 3A–C). Concerning to lipid peroxidation inhibition, as it happened for the capacity to scavenge free radicals, stem bark was also the most effective material, with an IC50 value of 197.33 ± 18.14 μg extract/mL (Fig. 3D). Comparing the obtained results with the positive control tested under the same conditions, we can observe that the antioxidant potential of both vegetal materials was higher than the observed for quercetin-3-O-rutinoside, commonly used as antioxidant for medical purposes (Kong et al., 2012), which exhibits IC50 values of 2364.00 ± 106.96, 26.00 ± 4.73 and 575.00 ± 27.93 a μg/mL against DPPH%, O2%− and %NO, respectively. The same did not happen for lipid peroxidation, for which quercetin (positive control) was more potent than the samples (IC50 value of 66.29 ± 3.13 μg/mL). The lipid peroxidation assay occurs in a lipophilic system and the aqueous extracts have components with hydrophilic characteristics, which can explain the lower capacity of both extracts comparatively to that of the positive control. The results obtained for the capacity to scavenge DPPH% and to inhibit lipid peroxidation were distinct from those previously described by Sultana et al. (2012), who found that the leaves from other cultivars were more active than the stem bark. In addition, the capacity of aqueous extracts from both materials to scavenge DPPH% was lower than that described for a hydroethanolic extract of mango leaves (IC50 value of 9.16 ± 0.19 μg/mL) (Pan et al., 2018). As far as we know, there is no available literature about the capacity of both vegetal materials to scavenge the O2%− and %NO in cell-free systems.

As we referred above, oxidative stress plays an essential role in the pathogenesis of both types of diabetes mellitus (Valko et al., 2006; Maritim et al., 2003; Pitocco et al., 2014). Indeed, there are scientific evidences that an increase in the production of high levels of reactive oxygen species is linked with glucose oxidation and noenzymatic glycation of proteins, which contribute to the development of diabetic complications (Maritim et al., 2003). One most challenging goal in the treatment of diabetes mellitus is the reduction of the blood glucose levels. α-Glucosidase and α-amylase are enzymes that catalyse the final step in the digestive process of carbohydrates and the hydrolysis of internal α-1,4-glucosidic linkage in polysaccharides, respectively (Kim et al., 2000). So, α-glucosidase and α-amylase inhibitors could suppress postprandial hyperglycaemia (Kim et al., 2000). In this work, the capacity of aqueous extracts from M. indica leaves and stem bark to inhibit both enzymes was evaluated. The two materials displayed a strong capacity to inhibit both enzymes, being more active against α-glucosidase (IC50 values of 4.47 ± 0.56 and 4.98 ± 0.74 extract μg/mL for leaves and stem bark, respectively) (Fig. 4). Leaves showed higher antidiabetic potential than stem bark, unlike what happened for antioxidant activity. Interestingly, aqueous extracts from M. indica leaves and stem bark revealed to be more potent α-glucosidase inhibitors than acarbose (positive control tested under the same conditions), which showed an IC50 value of 356.00 ± 20.58 μg/mL. Concerning to αamylase, acarbose (IC50 value of 1.40 ± 0.10 μg/mL) was more potent than the aqueous extracts from leaves and stem bark (IC50 values of 69.00 ± 1.53 and 135 ± 13.32 μg extract/mL, respectively). The α-glucosidase and α-amylase inhibitory effects of the aqueous extract from M. indica stem bark observed in this study were stronger than those reported in the literature for an ethanol and extract of other mango variety (Prashant et al., 2001a,b). According to those studies, an IC50 value of 314 μg/mL and an inhibition of 84.1% (1 mg/mL) was 289

Industrial Crops & Products 124 (2018) 284–293

D.G. Mouho et al.

Fig. 4. Effects of M. indica var. Nunkourouni leaves and stem bark aqueous extracts against: (A) α-glucosidase and, (B) α-amylase. Values show mean ± SD from three experiments performed in triplicate.

the leaf was cytotoxic for concentrations higher than 250 μg/mL, showing an IC50 value of 684.87 ± 29.02 μg/mL (Fig. 5A). On the other hand, the aqueous extract prepared from the stem bark was only cytotoxic for the higher tested concentration (Fig. 5A). Comparing our results with the ones obtained by Kim et al. (2010) for the same cell line, we can observe that the aqueous extract from the leaf is more cytotoxic than the hydroethanolic extract from mango flesh. As the mitochondrial activity was affected for the higher tested concentrations, we have also considered relevant to study the membrane integrity, which was evaluated by measuring the release of LDH. The obtained results showed that the loss of cell viability reflected by the MTT assay was not accompanied by elevated levels of LDH in the culture medium (Fig. 5B). Therefore, it can be concluded that none of the extracts lead to cell death by a necrotic process.

found for the α-glucosidase and α-amylase inhibition capacities, respectively (Prashant et al., 2001a,b). In addition, the capacity of the aqueous extract from M. indica leaves to inhibit the α-glucosidase found in this study was stronger than those described by Pan et al. (2018) for the hydroethanolic extract of mango leaves and their cyclohexane, ethyl acetate and n-butanol fractions (IC50 values of 235.41 ± 16.41, 106.40 ± 5.91, 82.78 ± 8.30 and 40.49 ± 0.43 μg/mL, respectively).

3.6. Effect on AGS cells Besides the involvement of oxidative stress in the progression of cancer diseases (Valko et al., 2006; Suzuki et al., 2012), namely the gastric one, which is the fourth most common cause of death by cancer worldwide (WHO, 2018), the presence of diabetes could also be relevant for the development of this type of cancer. Actually, some epidemiological studies indicate that the risk of gastric cancer could be increased in diabetic patients, since hyperglycaemia is associated with pro-inflammatory status, oxidative stress, impaired immune function and increased insulin secretion, and all of these conditions may contribute to the development of gastric cancer (Tseng and Tseng, 2014). Therefore, and taking into consideration that M. indica leaf and stem bark are traditionally consumed as infusion (Wong, 1976; Lauricella et al., 2017), the effect of both extracts on human gastric adenocarcinoma cells (AGS) was assessed for the first time. Aqueous extract from

3.7. Composition vs bioactivity Several researchers described that mangiferin is the compound responsible for the several bioactivities attributed to M. indica (Sanchez et al., 2000; Garrido et al., 2004). Thus, the strongest antioxidant capacity of stem bark could be partially attributed with high amounts of this C-glycosylated xanthone (Table 2). Indeed, it is well known the high potential of this metabolite to scavenge free radicals, such as DPPH % (Dar et al., 2005; Luo et al., 2012) as well as its protective effect in human umbilical vein endothelial (HUVEC) cells under H2O2-induced 290

Industrial Crops & Products 124 (2018) 284–293

D.G. Mouho et al.

Fig. 5. Effects of M. indica var. Nunkourouni leaves and stem bark aqueous extracts on the viability (A) and membrane integrity (B) of human gastric adenocarcinoma cells (AGS). Results are presented as mean ± standard error of the mean of four experiments, performed in triplicate. *p < 0.05, **p < 0.01 and ***p < 0.001, compared to the respective control.

2001). In addition, Sellamuthu et al. (2013) have also found that this xanthone protects streptozotocin-induced diabetic experimental rats against liver and kidney damage, by decreasing the oxidative markers levels and increasing the antioxidants systems (Sellamuthu et al., 2013). Besides its antioxidant properties, gallic acid is known to protect β-cells, increasing the plasma insulin levels and decreasing the blood glucose levels, and to increase the capacity of acarbose to inhibit αamylase and α-glucosidase (Punithavathi et al., 2011; Oboh et al., 2016). Thus, the greater amounts of gallic acid in leaves could be partially responsible for the higher antidiabetic potential of this vegetal material to inhibit both enzymes. The main phenolic compounds could also contribute for the cytotoxic effect of both extracts, mainly the leaves one. Indeed, gallic acid is known to inhibit AGS cells metastasis and invasive growth through the suppression of a number of signalling pathways (Ho et al., 2013). In addition, the anticancer potential of mangiferin is widely recognized by the scientific community, and this effect may be related with its capacity to induce the mitochondrial permeability (Pardo-Andreu et al., 2006). The presence of other phytochemicals could also contribute for the observed activities. For example, malic and citric acids, two of the most abundant organic acids in M. indica leaves and stem bark (Table 2), are known to be antioxidants by inhibiting the production of free radicals,

stress (Luo et al., 2012), suggesting its role in the prevention of oxidative stress-associated diseases. Moreover, its capacity to inhibit lipid peroxidation in rat liver microsomes was also described (Sato et al., 1992). According to several authors, the number of hydroxyl groups and the catechol moiety seem to be essential for its antioxidant potential (Dar et al., 2005). Besides mangiferin, the presence of other phenolic compounds could also contribute for the observed antioxidant activity. For example, the antioxidant properties of gallic acid, the main phenolic compound in the aqueous extract from the leaves (Table 2), are also known. Palafox-Carlos et al. (2012) studied the radical scavenging activity of four phenolic acids (gallic, protocatechuic, chlorogenic and vanillic) having observed that gallic acid was the most active one. According to those authors, the three hydroxyl groups available for hydrogen atom donation are essential for its high antioxidant potential (Palafox-Carlos et al., 2012). In addition, Punithavathi et al. (2011) demonstrated that gallic acid decreased streptozotocin induced oxidative stress, due to its ability to scavenge free radicals and to inhibit lipid peroxidation. The antidiabetic potential of both plant materials could also be partially related to the main phenolic compounds (mangiferin and gallic acid). Indeed, mangiferin is known to reduce the levels of blood glucose by inhibition of enzymes involved in the digestion of carbohydrates into simple sugars (Masibo and He, 2008; Aderibigbe et al., 291

Industrial Crops & Products 124 (2018) 284–293

D.G. Mouho et al.

such as hydroxyl radical (Seabra et al., 2006). Moreover, as extracts are complex mixtures, the presence of other non-determined metabolites and the synergistic and/or antagonistic interactions between the different compounds cannot be ignored.

Kim, H., Moon, J.Y., Kim, H., Lee, D.-S., Cho, M., Choi, H.Y., Kim, Y.S., Mosaddik, A., Cho, S.K., 2010. Antioxidant and antiproliferative activities of mango (Mangifera indica L.) flesh and peel. Food Chem. 121, 429–436. Kintzios, S., Papageorgioua, K., Yiakoumettis, I., Baricevi, D., Kusar, A., 2010. Evaluation of the antioxidants activities of four Slovene medicinal plant species by traditional and novel biosensory assays. J. Pharm. Biomed. Anal. 53, 773–776. Kong, K.W., Mat-Junit, S., Aminudin, N., Ismail, A., Abdul-Aziz, A., 2012. Antioxidant activities and polyphenolics from the shoots of Barringtonia racemosa (L.) Spreng in a polar to apolar medium system. Food Chem. 134, 324–332. Ksouri, R., Megdiche, W., Debez, A., Falleh, H., Grignon, C., Abdelly, C., 2007. Salinity effects on polyphenol content and antioxidant activities in leaves of the halophyte Cakile maritime. Plant Physiol. Biochem. 45, 244–249. Kulkarni, V.M., Rathod, V.K., 2014. Extraction of mangiferin from Mangifera indica leaves using three phase partitioning coupled with ultrasound. Ind. Crops Prod. 52, 292–297. Laskara, A., Alia, S.K., Siddiquib, S., 2017. The characterization of metal oxide - Mangifera indica L. matrix and its potential as scavenger of heavy metal pollutant Mohammad. Int. J. Environ. Stud. 74, 105–118. Lauricella, M., Emanuele, S., Calvaruso, G., Giuliano, M., D’Anneo, A., 2017. Multifaceted health benefits of Mangifera indica L. (Mango): the inestimable value of orchards recently planted in Sicilian rural areas. Nutrients 9, 525. https://doi.org/10.3390/ nu9050525. Liu, F.-X., Fu, S.-F., Bi, X.-F., Chen, F., Liao, X.-J., Hu, X.-S., Wu, J.-H., 2013. Physicochemical and antioxidant properties of four mango (Mangifera indica L.) cultivars in China. Food Chem. 138, 396–405. Luo, F., Lv, Q., Zhao, Y., Hu, G., Huang, G., Zhang, J., Sun, C., Li, X., Chen, K., 2012. Quantification and purification of mangiferin from Chinese Mango (Mangifera indica L.) cultivars and its protective effect on human umbilical vein endothelial cells under H2O2-induced stress. Int. J. Mol. Sci. 13, 11260–11274. Maritim, A.C., Sanders, R.A., Watkins, J.B., 2003. Diabetes, oxidative stress, and antioxidants: a review. J. Biochem. Mol. Toxicol. 17, 24–38. Masibo, M., He, Q., 2008. Major mango polyphenols and their potential significance to human health. Compr. Rev. Food Sci. Food Saf. 7, 309–319. Núñez Sellés, A.J., Vélez Castro, H.T., Agüero-Agüero, J., González-González, J., Naddeo, F., de Simone, F., Rastrelli, L., 2002. Isolation and quantitative analysis of phenolic antioxidants, free sugars, and polyols from mango (Mangifera indica L.) stem bark aqueous decoction used in Cuba as a nutritional supplement. J. Agric. Food Chem. 50, 762–766. Oboh, G., Ogunsuyi, O.B., Ogunbadejo, M.D., Adefegha, S.A., 2016. Influence of gallic acid on α-amylase and α-glucosidase inhibitory properties of acarbose. J. Food Drug Anal. 24, 627–634. Oliveira, A.P., Valentão, P., Pereira, J.A., Silva, B.M., Tavares, F., Andrade, P.B., 2009. Ficus carica L.: metabolic and biological screening. Food Chem. Toxicol. 47, 2841–2846. Palafox-Carlos, H., Yahia, E.M., González-Aguilar, G.A., 2012. Identification and quantification of major phenolic compounds from mango (Mangifera indica, cv. Ataulfo) fruit by HPLC-DAD-MS/MS-ESI and their individual contribution to the antioxidant activity during ripening. Food Chem. 135, 105–111. Pan, J., Yia, X., Zhang, S., Cheng, J., Wang, Y., Liu, C., He, X., 2018. Bioactive phenolics from mango leaves (Mangifera indica L.). Ind. Crops Prod. 111, 400–406. Pardo-Andreu, G.L., Dorta, D.J., Delgado, R., Cavalheiro, R.A., Santos, A.C., Vercesi, A.E., Curti, C., 2006. Vimang (Mangifera indica L. extract) induces permeability transition in isolated mitochondria, closely reproducing the effect of mangiferin, Vimang’s main component. Chem.-Biol. Interact. 159, 141–148. Pereira, R.B., Pinto, D.G.A., Pereira, D.M., Gomes, N.G.M., Silva, A.M.S., Andrade, P.B., Valentão, P., 2017. UHPLC-MS/MS profiling of Aplysia depilans and assessment of its potential therapeutic use: interference on iNOS expression in LPS-stimulated RAW 264.7 macrophages and caspase-mediated pro-apoptotic effect on SH-SY5Y cells. J. Funct. Food. 37, 164–175. Pitocco, D., Martini, F., Scavone, G., Zaccardi, F., Ghirlanda, G., 2014. Oxidative stress and diabetes. In: Laher, I. (Ed.), Systems Biology of Free Radicals and Antioxidants. Springer, Berlin, Heidelberg. Prashant, D., Amit, A., Samiulla, D.S., Asha, M.K., Padmaja, R., 2001a. α-Glucosidase inhibitory activity of Mangifera indica bark. Fitoterapia 72, 686–688. Prashanth, D., Padmaja, R., Samiulla, D.S., 2001b. Effect of certain plant extracts on αamylase activity. Fitoterapia 72, 179–181. Punithavathi, V.R., Prince, P.S.M., Kumar, R., Selvakumari, J., 2011. Antihyperglycaemic, antilipid peroxidative and antioxidant effects of gallic acid on streptozotocin induced diabetic Wistar rats. Eur. J. Pharmacol. 650, 465–471. Rey, J.-Y., Diallo, T.M., Vannière, H., Didier, C., Kéitac, S., Sangaré, M., 2004. La mangue en Afrique de l’Ouest francophone: variétés et composition variétale des vergers. Fruits 59, 191–208. Ribeiro, S.M.R., Barbosa, L.C.A., Queiroz, J.H., Knödler, M., Schieber, A., 2008. Phenolic compounds and antioxidant capacity of Brazilian mango (Mangifera indica L.) varieties. Food Chem. 110, 620–626. Romero, J.A., Vandama, R., López, M., Capote, M., Ferradá, C., Carballo, C., Delgado, R., Berghe, W.V., Apers, S., 2015. Study of physicochemical parameters of different cultivars of Mangifera indica L. leaves for their use as a source of mangiferin. Int. J. Pharm. Phytochem. Res. 7, 608–612. Sairam, K., Hemalatha, S., Kumar, A., Srinivasan, T., Ganesh, J., Shankar, M., Venkataraman, S., 2003. Evaluation of anti-diarrhoeal activity in seed extracts of Mangifera indica. J. Ethnopharmacol. 84, 11–15. Saleh, N.A.M., El-Ansari, M.A.I., 1975. Polyphenolics of twenty local verities of Mangifera indica. Planta Med. 28, 124–130. Sanchez, G.M., Re, L., Giuliani, A., Nunez-Selles, A.J., Davison, G.P., Leon-Fernandez, O., 2000. Protective effects of Mangifera indica L. extract, mangiferin and selected

4. Conclusion In conclusion, analytical methods were successfully employed in the analysis of the phenolic compounds and organic acids found in the aqueous extract of leaf and stem bark from M. indica var. Nunkourouni, which are reported for the first time. The antioxidant, antidiabetic and cytotoxic properties on AGS cells, also assessed for the first time, seem to be essentially related with the main phenolic compounds. As the aqueous extracts showed to be able to scavenge free radicals and to decrease blood glucose levels, the risk of developing cancer, namely the gastric one, may be lower. Moreover, both extracts could be beneficial for patients with diabetes and gastric cancer, due to their capacity to inhibit enzymes involved in diabetes disease and to their cytotoxic effects in AGS cells. Therefore, the fallen leaves of M. indica, discarded as waste, and the stem bark may be used for compounds isolation and/or incorporated in the diet as a functional food or nutraceutical and could be useful to prevent and/or treat human diseases. Acknowledgements This work received financial support from National Funds (FCT/ MEC, Fundação para a Ciência e Tecnologia/Ministério da Educação e Ciência) through project UID/QUI/50006/2013, co-financed by European Union (FEDER under the Partnership Agreement PT2020), from Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) (project NORTE-010145-FEDER-000024), and from Programa de Cooperación Interreg V-A España – Portugal (POCTEP) 2014-2020 (project 0377_IBERPHENOL_6_E). To all financing sources the authors are greatly indebted. Didier G. Mouho received financial support from European Union (EU) in the framework of the project KITE Erasmus Mundus Action II – lot 18 ACP (2013-2017). Andreia P. Oliveira (SFRH/ BPD/96819/2013) thanks FCT for the grant. References Aderibigbe, A.O., Emudianughe, T.S., Lawal, B.A., 2001. Evaluation of the antidiabetic action of Mangifera indica in mice. Phytother. Res. 15, 456–458. Barreto, J.C., Trevisan, M.T.S., Hull, W.E., Erben, G., de Brito, E.S., Pfundstein, B., Würtele, G., Spiegelhalder, B., Owen, R.W., 2008. Characterization and quantitation of polyphenolic compounds in bark, kernel, leaves, and peel of mango (Mangifera indica L.). J. Agric. Food Chem. 56, 5599–5610. Dar, A., Faizi, S., Naqvi, S., Roome, T., Zikr-ur-Rehman, S., Ali, M., Firdous, S., Moin, S.T., 2005. Analgesic and antioxidant activity of mangiferin and its derivatives: the structure activity relationship. Biol. Pharm. Bull. 28, 596–600. Ferreres, F., Lopes, G., Gil-Izquierdo, A., Andrade, P.B., Sousa, C., Mouga, T., Valentão, P., 2012. Phlorotannin extracts from Fucales characterized by HPLC-DAD-ESI-MSn: approaches to hyaluronidase inhibitory capacity and antioxidant properties. Mar. Drugs 10, 2766–2781. Figueiredo-González, M., Grosso, C., Valentão, P., Andrade, P.B., 2016. α-Glucosidase and α-amylase inhibitors from Myrcia spp.: a stronger alternative to acarbose? J. Pharm. Biomed. Anal. 118, 322–327. Figueiredo-González, M., Valentão, P., Andrade, P.B., 2017. Tomato plant leaves: from by-products to the management of enzymes in chronic diseases. Ind. Crops Prod. 94, 621–629. Garrido, G., González, D., Lemusa, Y., García, D., Lodeiro, L., Quintero, G., Delporte, C., Núñez-Sellés, A.J., Delgado, R., 2004. In vivo and in vitro anti-inflammatory activity of Mangifera indica L. extract (VIMANG®). Pharmacol. Res. 50, 143–149. Ho, H.-H., Chang, C.-S., Ho, W.-C., Liao, S.-Y., Lin, W.-L., Wang, C.-J., 2013. Gallic acid inhibits gastric cancer cells metastasis and invasive growth via increased expression of RhoB, downregulation of AKT/small GTPase signals and inhibition of NF-κB activity. Toxicol. Appl. Pharmacol. 266, 76–85. Jahurul, M.H.A., Zaidul, I.S.M., Ghafour, K., Al-Juhaimi, F.Y., Nyam, K.-L., Norulaini, N.A.N., Sahena, F., Ohmar, A.K.M., 2015. Mango (Mangifera indica L.) by-products and their valuable components: a review. Food Chem. 183, 173–180. Kim, J.-S., Kwon, C.-S., Son, H.K., 2000. Inhibition of α-glucosidase and amylase by luteolin, a flavonoid. Biosci. Biotechnol. Biochem. 64, 2458–2461.

292

Industrial Crops & Products 124 (2018) 284–293

D.G. Mouho et al.

Suzuki, H., Nisizawa, T., Tsugawa, H., Mogami, S., Hibi, T., 2012. Roles of oxidative stress in stomach disorders. J. Clin. Biochem. Nutr. 50, 35–39. Tharanathan, R.N., Yashoda, H.M., Prabha, T.N., 2006. Mango (Mangifera indica L.), “The king of fruits”-an overview. Food Rev. Int. 22, 95–123. Treutter, D., 2006. Significance of flavonoids in plant resistance: a review. Environ. Chem. Lett. 4, 147–157. Tseng, C.-H., Tseng, F.-H., 2014. Diabetes and gastric cancer: the potential links. World J. Gastroenterol. 20, 1701–1711. Valko, M., Rhodes, C.J., Moncol, J., Izakovic, M., Mazur, M., 2006. Free radicals, metals and antioxidants in oxidative stress-induced cancer. Chem.-Biol. Interact. 160, 1–40. Wauthoz, N., Balde, A., Balde, E.S., Damme, M.V., Duez, P., 2007. Ethnopharmacology of Mangifera indica L. bark and pharmacological studies of its main C-glucosylxanthone, mangiferin. Int. J. Biomed. Pharm. Sci. 1, 112–119. WHO, 2018. Cancer. Available at:. (Accessed 6 June 2018). http://www.who.int/newsroom/fact-sheets/detail/cancer. Wong, W., 1976. Some folk medicinal plants from Trinidad. Econ. Bot. 30, 103–142. Zeković, Z., Cvetanović, A., Švarc-Gajić, J., Gorjanović, S., Sužnjević, D., Mašković, P., Savić, S., Radojković, M., Durović, S., 2017. Chemical and biological screening of stinging nettle leaves extracts obtained by modern extraction techniques. Ind. Crops Prod. 108, 423–430.

antioxidants against TPA-induced biomolecules oxidation and peritoneal macrophage activation in mice. Pharmacol. Res. 42, 565–573. Santana-Méridas, O., González-Coloma, A., Sánchez-Vioque, R., 2012. Agricultural residues as a source of bioactive natural products. Phytochem. Rev. 11, 447–466. Sato, T., Kawamoto, A., Tamura, A., Tatsumi, Y., Fujii, T., 1992. Mechanism of antioxidant action of pueraria glycoside (PG)-1 (an isoflavonoid) and mangiferin (a xanthonoid). Chem. Pharm. Bull. 40, 721–724. Scalbert, A., Williamson, G., 2000. Dietary intake and bioavailability of polyphenols. J. Nutr. 130, 2073–2085. Seabra, R.M., Andrade, P.B., Valentão, P., Fernandes, E., Carvalho, F., Bastos, M.L., 2006. Anti-oxidant compounds extracted from several plant materials. Biomaterials from Aquatic and Terrestrial Organisms. Science Publishers–Enfield (NH) Jersey Plymouth, New Hampshire. Sellamuthu, P.S., Arulselvan, P., Kamalraj, S., Fakurazi, S., Kandasamy, M., 2013. Protective nature of mangiferin on oxidative stress and antioxidant status in tissues of streptozotocin-induced diabetic rats. ISRN Pharmacol. 750109. Singh, Y.N., 1986. Traditional medicine in Fiji. Some herbal folk cures used by Fiji Indians. J. Ethnopharmacol. 15, 57–88. Sultana, B., Hussain, Z., Asif, M., Munir, A., 2012. Investigation on the antioxidant activity of leaves, peels, stems bark, and kernel of mango (Mangifera indica L.). J. Food Sci. 77, C849–C852.

293