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Assessing antioxidant capacity in plant foods
CONCEPTS AND CONSIDERATIONS ON THE HEALTH BENEFITS OF PHYTOCHEMICALS AND FUNCTIONAL FOODS k,@eevBlumbere Tufls Uniuersity, Boston, MA 02111. The concept of what foods can provide has changed from its previous emphasis on health maintenance through recommended nutrient allowances and dietary guidelines to a focus on the promising use of foods prepared with enhanced or novel phytochemicals, particularly ones with antioxidant capacity, to promote health and reduce the risk of chronic diseases. Dietary antioxidants have recently been defined as substances in foods that significantly decrease the adverse effects of reactive oxygen species, reactive nitrogen species, or both on normal physiological function in humans. Phenols and polyphenols are widely distributed in plant foods. They possess antioxidant activity in vitro and appear to elicit biological effects consistent with improved human health noted in several observational studies, particularly a reduced risk of cancer and cardiovascular disease. However, in contrast to antioxidant carotenoids, comprehensive food composition data for these compounds remain unavailable for extensive epidemiological investigations and limited clinical data are available on the bioavailability and metabolism of these components. While measures of oxidative stress status and intermediary biomarkers of disease are suitable to define these phytochemicals as antioxidants in animal models and human studies, conclusive substantiation of the health benefits of these phytonutrients will require clinical trials employing physiological functions and disease endpoints as outcomes. The incorporation of antioxidant phytochemicals into the development of functional foods appears to provide a practical preventive nutrition approach to promote optimal health.
Assessing Antioxidant Capacity in Plant Foods. Ronald L. Prior and G. Cao. USDA Human Nutrition Research Center on Aging at Tufts Univ., 711 Washington Street, Boston, MA 02 111 Free radicals and other reactive species are considered to be important causative factors in the development of diseases of aging such as cancer and cardiovascular diseases. This has led to considerable interest in assessing the antioxidant capacity of plant foods. The Oxygen Radical Absorbance Capacity (ORAC) assay has been used as a tool for antioxidant assessment of plant foods. TheORACprocedureusesAAeH[2,2’-azohis(2-amidinopropane) dihydrochloride] as a peroxyl radical source, which is relevant to biological systems since the peroxyl radical is the most abundant free radical. Other oxidant sources (hydroxyl radical and Cut+) can also be utilized to characterize antioxidants in plant foods. However, free radical or oxidant source is important and direct comparisons cannot be made between procedures that use different sources. Antioxidant capacity has been measured in over SO common foods with more than a 20-fold difference observed in the different fresh fruits and vegetables. Phenolic acids and such as flavonols, anthocyanins and polyphenolics proanthocyanins are responsible for a majority of the antioxidant capacity in fruits and vegetables. Although little is known about the absorption and metabolism of these antioxidant components, improvement in the in viva antioxidant status has been observed in human subjects following increased consumption of fruits and vegetables. The ORAC method provides a basis from which to establish dietary intakes that might impact health outcomes.
II P-20 I
IP-19
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HOW DO ISOFLAVONES
REALLY WORK? S. Barnes, B. Boersma, R. Patel, M Kirk, H. Kim, J. Xu, and V. M. Darley-Usmar. Depts Pathol., Pharmacol. & Toxic& and Comprehensive Cancer Center Mass Spec. Shared Facility, University of Alabama at Birmingham, Birmingham, AL 35294. Genistein (5,7,4’-trihydroxyisoflavone) (GEN) is associated with lowered risk of several chronic diseases. Long known for its estrogenic properties, GEN binds to estrogen receptor beta (ERg) It is also a with an tinity that is close to that of 17p-estradiol. protein tyrosine kinase (PTK) inhibitor. However, in some cells GEN may not directly inhibit PTK enzyme activities, but rather downregulates their expression. Other potential mechanisms of action of GEN involve upregulation of TGF beta expression (thereby controlling cell proliferation, pticularly in the vascular system, and angiogenesis), effects on ion transport systems and its interaction with cellular oxidants. GEN and other bioflavonoids can interact with cellular and vascular space oxidants, thereby protecting critical biochemical targets such as LDL. However, the production of oxidants may substantially exceed the capacity of the bioflavonoids to remove them in vivo. In a novel hypothesis, we have proposed that the products of the reactions between reactive oxygen species and bioflavonoids will have altered interaction with their receptor protein targets. Thus, when an isoflavone is oxidized, one or more of its oxidized metabolites may have a higher affinity to ERa/ER@ or other receptor targets than the unmodified isoflavone. Accordingly, the effect of genistein may be locally enhanced in tissues where oxidants are produced. In summary, GEN and related bioflavonoids have several related mechanisms that may explain their widespread estrogen-like and non-estrogen-like responses in biological systems.
OXYGEN
THE ANALYSIS OF OLIGOMERIC PROCYANDINS PLANT FOODS BY HPLC/MS John F. Hammerstone,
IN
Sheryl A. Lazarus, Gary E. Adamson
Mars, Inc., Hackettstown,
NJ 07840
In the current study, we investigated the usefulness of reversed-phase and normal-phase high performance liquid chromatography (HPLC) coupled with on-line mass spectrometry (MS) for comparing the separation of low molecular weight flavonoids versus the oligomeric procyanidins. The results of this study demonstrated that the reversed-phase technique was better suited for the separation of the monomeric flavan-3-01s and flavonols, such as those found in green tea, while the normal-phase method was superior for separation of the flavan-3-01 oligomers, such as those found in cocoa. Subsequently, the normal-phase HPLC method was applied to the analysis of monomeric and oligomeric proanthocyanidins present in a range of plant derived foods and beverages. In addition, UV and fluorescence detection were used to monitor the separation of proanthocyanidins. This qualitative report demonstrates the ability of this normal-phase HPLC/MS technique to separate singly and doubly linked procyanidins, prodelphinidins and copolymer oligomers, including their gallic acid esters present in a range of food and beverage samples using a normal-phase separation. Finally, fluorescence detection demonstrated both increased sensitivity and selectivity towards procyanidins as compared to UV detection.
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Assessing Antioxidant Capacity in Plant Foods. Ronald L. Prior and G. Cao. USDA Human Nutrition Research Center on Aging at Tufts Univ., 711 Washington Street, Boston, MA 02 111 Free radicals and other reactive species are considered to be important causative factors in the development of diseases of aging such as cancer and cardiovascular diseases. This has led to considerable interest in assessing the antioxidant capacity of plant foods. The Oxygen Radical Absorbance Capacity (ORAC) assay has been used as a tool for antioxidant assessment of plant foods. TheORACprocedureusesAAeH[2,2’-azohis(2-amidinopropane) dihydrochloride] as a peroxyl radical source, which is relevant to biological systems since the peroxyl radical is the most abundant free radical. Other oxidant sources (hydroxyl radical and Cut+) can also be utilized to characterize antioxidants in plant foods. However, free radical or oxidant source is important and direct comparisons cannot be made between procedures that use different sources. Antioxidant capacity has been measured in over SO common foods with more than a 20-fold difference observed in the different fresh fruits and vegetables. Phenolic acids and such as flavonols, anthocyanins and polyphenolics proanthocyanins are responsible for a majority of the antioxidant capacity in fruits and vegetables. Although little is known about the absorption and metabolism of these antioxidant components, improvement in the in viva antioxidant status has been observed in human subjects following increased consumption of fruits and vegetables. The ORAC method provides a basis from which to establish dietary intakes that might impact health outcomes.
II P-20 I
IP-19
I
HOW DO ISOFLAVONES
REALLY WORK? S. Barnes, B. Boersma, R. Patel, M Kirk, H. Kim, J. Xu, and V. M. Darley-Usmar. Depts Pathol., Pharmacol. & Toxic& and Comprehensive Cancer Center Mass Spec. Shared Facility, University of Alabama at Birmingham, Birmingham, AL 35294. Genistein (5,7,4’-trihydroxyisoflavone) (GEN) is associated with lowered risk of several chronic diseases. Long known for its estrogenic properties, GEN binds to estrogen receptor beta (ERg) It is also a with an tinity that is close to that of 17p-estradiol. protein tyrosine kinase (PTK) inhibitor. However, in some cells GEN may not directly inhibit PTK enzyme activities, but rather downregulates their expression. Other potential mechanisms of action of GEN involve upregulation of TGF beta expression (thereby controlling cell proliferation, pticularly in the vascular system, and angiogenesis), effects on ion transport systems and its interaction with cellular oxidants. GEN and other bioflavonoids can interact with cellular and vascular space oxidants, thereby protecting critical biochemical targets such as LDL. However, the production of oxidants may substantially exceed the capacity of the bioflavonoids to remove them in vivo. In a novel hypothesis, we have proposed that the products of the reactions between reactive oxygen species and bioflavonoids will have altered interaction with their receptor protein targets. Thus, when an isoflavone is oxidized, one or more of its oxidized metabolites may have a higher affinity to ERa/ER@ or other receptor targets than the unmodified isoflavone. Accordingly, the effect of genistein may be locally enhanced in tissues where oxidants are produced. In summary, GEN and related bioflavonoids have several related mechanisms that may explain their widespread estrogen-like and non-estrogen-like responses in biological systems.
OXYGEN
THE ANALYSIS OF OLIGOMERIC PROCYANDINS PLANT FOODS BY HPLC/MS John F. Hammerstone,
IN
Sheryl A. Lazarus, Gary E. Adamson
Mars, Inc., Hackettstown,
NJ 07840
In the current study, we investigated the usefulness of reversed-phase and normal-phase high performance liquid chromatography (HPLC) coupled with on-line mass spectrometry (MS) for comparing the separation of low molecular weight flavonoids versus the oligomeric procyanidins. The results of this study demonstrated that the reversed-phase technique was better suited for the separation of the monomeric flavan-3-01s and flavonols, such as those found in green tea, while the normal-phase method was superior for separation of the flavan-3-01 oligomers, such as those found in cocoa. Subsequently, the normal-phase HPLC method was applied to the analysis of monomeric and oligomeric proanthocyanidins present in a range of plant derived foods and beverages. In addition, UV and fluorescence detection were used to monitor the separation of proanthocyanidins. This qualitative report demonstrates the ability of this normal-phase HPLC/MS technique to separate singly and doubly linked procyanidins, prodelphinidins and copolymer oligomers, including their gallic acid esters present in a range of food and beverage samples using a normal-phase separation. Finally, fluorescence detection demonstrated both increased sensitivity and selectivity towards procyanidins as compared to UV detection.
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9
Sll