Abstract: In this study, six common tests for measuring antioxidant activity were evaluated by comparing four antioxidants and applying them to beverages (tea and juices): Trolox equivalent antioxidant capacity assay (TEAC I-III assay), Total radical-trapping antioxidant parameter assay (TRAP assay), 2,2-diphenyl-l-picrylhydrazyl assay (DPPH assay), N,N-dimethyl-p-phenylendiamine assay (DMPD assay), Photochemiluminescence assay (PCL assay) and Ferric reducing ability of plasma assay (FRAP assay) The antioxidants included gallic acid representing the group of polyphenols, uric acid as the main antioxidant in human plasma, ascorbic acid as a vitamin widely spread in fruits and Trolox as water soluble vitamin E analogue The six methods presented can be divided into two groups depending on the oxidising reagent Five methods use organic radical producers (TEAC I-III, TRAP, DPPH, DMPD, PCL) and one method works with metal ions for oxidation (FRAP) Another difference between these tests is the reaction procedure Three assays use the delay in oxidation and determine the lag phase as parameter for the antioxidant activity (TEAC I, TRAP, PCL) They determine the delay of radical generation as well as the ability to scavenge the radical In contrast, the assays TEAC II and III, DPPH, DMPD and FRAP analyse the ability to reduce the radical cation (TEAC II and III, DPPH, DMPD) or the ferric ion (FRAP) The three tests acting by radical reduction use preformed radicals and determine the decrease in absorbance while the FRAP assay measures the formed ferrous ions by increased absorbance Gallic acid was the strongest antioxidant in all tests with exception of the DMPD assay In contrast, uric acid and ascorbic acid showed low activity in some assays Most of the assays determine the antioxidant activity in the micromolar range needing minutes to hours Only one assay (PCL) is able to analyse the antioxidant activity in the nanomolar range Black currant juice showed highest antioxidant activity in all tests compared to tea, apple juice and tomato juice Despite these differences, results of these in vitro assays give an idea of the protective efficacy of secondary plant products It is strongly recommended to use at least two methods due to the differences between the test systems investigated

Abstract: Green tea and tea polyphenols have been studied extensively as cancer chemopreventive agents in recent years. The bioavailability and metabolic fate of tea polyphenols in humans, however, are not clearly understood. In this report, the pharmacokinetic parameters of (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin (EC) were analyzed after administration of a single oral dose of green tea or decaffeinated green tea (20 mg tea solids/kg) or EGCG (2 mg/kg) to eight subjects. The plasma and urine levels of total EGCG, EGC, and EC (free plus conjugated forms) were quantified by HPLC coupled to an electrochemical detector. The plasma concentration time curves of the catechins were fitted in a one-compartment model. The maximum plasma concentrations of EGCG, EGC, and EC in the three repeated experiments with green tea were 77.9 +/- 22.2, 223.4 +/- 35.2, and 124.03 +/- 7.86 ng/ml, respectively, and the corresponding AUC values were 508.2 +/- 227, 945.4 +/- 438.4, and 529.5 +/- 244.4 ng x h x ml(-1), respectively. The time needed to reach the peak concentrations was in the range of 1.3-1.6 h. The elimination half-lives were 3.4 +/- 0.3, 1.7 +/- 0.4, and 2.0 +/- 0.4 h, respectively. Considerable interindividual differences and variations between repeated experiments in the pharmacokinetic parameters were noted. Significant differences in these pharmacokinetic parameters were not observed when EGCG was given in decaffeinated green tea or in pure form. In the plasma, EGCG was mostly present in the free form, whereas EGC and EC were mostly in the conjugated form. Over 90% of the total urinary EGC and EC, almost all in the conjugated forms, were excreted between 0 and 8 h. Substantial amounts of 4'-O-methyl EGC, at levels higher than EGC, were detected in the urine and plasma. The plasma level of 4'-O-methyl EGC peaked at 1.7 +/- 0.5 h with a half life of 4.4 +/- 1.1 h. Two ring-fission metabolites, (-)-5-(3',4',5'-trihydroxyphenyl)-gamma-valerolactone (M4) and (-)-5-(3',4'-dihydroxyphenyl)-valerolactone (M6), appeared in significant amounts after 3 h and peaked at 8-15 h in the urine as well as in the plasma. These results may be useful for designing the dose and dose frequency in intervention studies with tea and for development of biomarkers of tea consumption.

Abstract: Polyphenols are largely responsible for the astringency and “mouthfeel” of tea and wine by their interactions with basic salivary proline-rich proteins. Astringency arises from precipitation of polyphenol/peptide complexes, which is an important protective mechanism in animals that consume polyphenols. This paper presents biophysical studies of the interactions between chemically defined polyphenols and peptides. It is shown that intermolecular binding is dominated by stacking of polyphenolic rings onto planar hydrophobic surfaces and is strengthened by multiple cooperative binding of polyphenolic rings. Affinities weaken at higher temperatures and are unaffected by pH between pH 3.8 and 6.0. Measurements of self-diffusion rates for peptides with increasing concentrations of polyphenol demonstrate that peptides become increasingly coated with polyphenol. When the coating is sufficiently extensive to provide cooperative polyphenol bridges, the peptide dimerizes and precipitates. Light scattering measuremen...

Abstract: Ellagic acid, a plant-derived polyphenol, inhibits gamma-radiation (hydroxyl radical) induced lipid peroxidation in rat liver microsomes in a dose- and concentration-dependent manner. Its antioxidant capacity has been estimated using the 1,1-diphenyl-2-picrylhydrazyl radical assay. To understand the actual mechanisms involved in antioxidant activity and the free radical scavenging ability,a nanosecond pulse radiolysis technique has been employed. The rate constants for the reactions of several reactive oxygen species and reactive nitrogen species such as hydroxyl, peroxyl, and nitrogen dioxide radicals have been found to be in the range of 10(6)-10(9) M(-1) s(-1). The ellagic acid radicals have been characterized by the absorption spectra and decay kinetics. Studies on the reactions of ellagic acid with the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) radical and the radicals of ellagic acid with ascorbate have been used to estimate its one-electron reduction potential. Ellagic acid has also been found to be a good scavenger of peroxynitrite. Using stopped-flow reaction analyzer with absorption detection, the rate constant for this reaction has been determined to be 3.7 x 10(3) M(-1) s (-1). The electron spin resonance spectra of the oxidized ellagic acid radicals have been recorded by horseradish peroxidase and hydrogen peroxide method.

Abstract: Most plant-derived polyphenols exhibit strong antioxidant potentials, established by various assay procedures. With pulse radiolysis experiments, absolute scavenging rate constants can be obtained with a variety of oxidizing radicals which allow further structure-activity correlations and, combined with EPR spectroscopy, detailed insight into the mechanisms governing these antioxidant reactions. The most striking difference occurs between regular flavonoids and both condensed and hydrolyzable tannins. The tannins are considered superior antioxidants as their eventual oxidation may lead to oligomerization via phenolic coupling and enlargement of the number of reactive sites, a reaction which has never been observed with the flavonoids themselves.

Abstract: A widely used method for analyzing hydrolyzable tannins afer reaction with KIO3 has been modified to include a methanolysis step followed by oxidation with KIO3. In the new method, hydrolyzable tannins (gallotannins and ellagitannins) are reacted at 85 °C for 20 h in methanol/sulfuric acid to quantitatively release methyl gallate. Dried plant samples can be methanolyzed under the same conditions to convert hydrolyzable tannins to methyl gallate. Oxidation of the methyl gallate by KIO3 at pH 5.5, 30 °C, forms a chromophore with λmax 525 nm, which is determined spectrophotometrically. The detection limit of the method is 1.5 μg of methyl gallate, and with plant samples, relative standard deviations of less than 3% were obtained. Keywords: Tannin; polyphenolic compound; hydrolyzable tannin; methyl gallate; galloyl glucose; gallotannin; potassium iodate

Abstract: The beneficial health effects attributed to the consumption of fruit and vegetables are related, at least in part, to their antioxidant activity. Of special interest is the inverse relationship between the intake of dietary nutrients rich in polyphenols and cardiovascular diseases. This effect is attributed to polyphenols' ability to inhibit low-density lipoprotein (LDL) oxidation, macrophage foam cell formation and atherosclerosis. Pomegranate polyphenols can protect LDL against cell-mediated oxidation via two pathways, including either direct interaction of the polyphenols with the lipoprotein and/or an indirect effect through accumulation of polyphenols in arterial macrophages. Pomegranate polyphenols were shown to reduce the capacity of macrophages to oxidatively modify LDL, due to their interaction with LDL to inhibit its oxidation by scavenging reactive oxygen species and reactive nitrogen species and also due to accumulation of polyphenols in arterial macrophages; hence, the inhibition of macrophage lipid peroxidation and the formation of lipid peroxide-rich macrophages. Furthermore, pomegranate polyphenols increase serum paraoxonase activity, resulting in the hydrolysis of lipid peroxides in oxidized lipoproteins and in atherosclerotic lesions. These antioxidative and antiatherogenic effects of pomegranate polyphenols were demonstrated in vitro, as well as in vivo in humans and in atherosclerotic apolipoprotein E deficient mice. Dietary supplementation of polyphenol-rich pomegranate juice to atherosclerotic mice significantly inhibited the development of atherosclerotic lesions and this may be attributed to the protection of LDL against oxidation.

Abstract: Antioxidant properties of flavonoids and ellagic acid were characterized in eight wines and juices produced by various processing methodologies from red and white muscadine grape cultivars (Vitis rotundifolia). Juices and wines were produced by hot- and cold-pressed techniques, and additional wine was produced following on-hull fermentation for 3, 5, and 7 days. Chromatographic conditions were developed to simultaneously separate anthocyanins, ellagic acid, and flavonols and correlated to a measurement of overall antioxidant capacity (AOX), and their changes were monitored after storage for 60 days at 20 and 37 °C. Regression coefficients between concentrations of individual polyphenolics and AOX ranged from 0.55 for ellagic acid to 0.90 for kaempferol. Both red and white wines had higher AOX values after storage than juices made from an identical grape press, despite lower concentrations of individual polyphenolic compounds. Red wines fermented on-hull had higher initial concentrations of antioxidant pol...

Abstract: Separation, identification and quantification of polyphenols was carried out on leaves of Pistacia lentiscus L., an evergreen member of the family Anacardiaceae, using semi-preparative HPLC, HPLC-photodiode array detection and HPLC-MS analysis, together with 1H- and 13C NMR. Three major classes of secondary metabolites were detected: (i) gallic acid and galloyl derivatives of both glucose and quinic acid; (ii) flavonol glycosides, i.e. myricetin and quercetin glycosides; and (iii) anthocyanins, namely delphinidin 3-O-glucoside and cyanidin 3-O-glucoside. Low amounts of catechin were also detected. The concentration of galloyl derivatives was extremely high, representing 5.3% of the leaf dry weight, and appreciable amounts of myricetin derivatives were also detected (1.5% on a dry weight basis). These findings may be useful in establishing a relationship between the chemical composition of the leaf extract and the previously reported biological activity of P. lentiscus, and may also assign a new potential role of P. lentiscus tissue extracts in human health care. Copyright © 2002 John Wiley & Sons, Ltd.

Abstract: Phenols are universal components of plant material. Flavonoids are polyphenolic constituents of the diet with antioxidant properties by virtue of the structural arrangements and hydrogen-donating potential of their phenolic groups. The ability of specific phenolics to chelate transition metal ions is also of significance. In vitro , the antioxidant activity of the aglycone forms of these polyphenols is, in the main, greater than that of vitamin E and vitamin C. In the diet they are present principally as glycosylated, esterified or polymerized derivatives. Many factors, such as the extent of their gastrointestinal absorption, metabolism (possibly into derivatives with enhanced activity) and interaction with target cells, affect the bioavailability and activity of dietary polyphenols. The balance between beneficial and detrimental effects after their consumption is thus somewhat unpredictable. The possible sites at which these compounds might act as significant dietary micronutrient antioxidants are: (1) i...

Abstract: Oligomeric proanthocyanidins constitute a group of water-soluble polyphenolic tannins that are present in the female inflorescences (up to 5% dry wt) of the hop plant (Humulus lupulus). Humans are exposed to hop proanthocyanidins through consumption of beer. Proanthocyanidins from hops were characterized for their chemical structure and their in vitro biological activities. Chemically, they consist mainly of oligomeric catechins ranging from dimers to octamers, with minor amounts of catechin oligomers containing one or two gallocatechin units. The chemical structures of four procyanidin dimers (B1, B2, B3, and B4) and one trimer, epicatechin-(4beta-->8)-catechin-(4alpha-->8)-catechin (TR), were elucidated using mass spectrometry, NMR spectroscopy, and chemical degradation. When tested as a mixture, the hop oligomeric proanthocyanidins (PC) were found to be potent inhibitors of neuronal nitric oxide synthase (nNOS) activity. Among the oligomers tested, procyanidin B2 was most inhibitory against nNOS activity. Procyanidin B3, catechin, and epicatechin were noninhibitory against nNOS activity. PC and the individual oligomers were all strong inhibitors of 3-morpholinosydnonimine (SIN-1)-induced oxidation of LDL, with procyanidin B3 showing the highest antioxidant activity at 0.1 microg/mL. The catechin trimer (TR) exhibited antioxidant activity more than 1 order of magnitude greater than that of alpha-tocopherol or ascorbic acid on a molar basis.

Abstract: The phenolic composition and antioxidant activities [TEAC, ORAC, FRAP] of consumer brews (1 tea bag in 230 ml for 1 min) of seven different brands of black tea from the British market were investigated The main phenolic compounds identified were epigallocatechin gallate, four theaflavins, as well as epicatechin gallate, theogallin (tentative assignment), quercetin-3-rutinoside and 4-caffeoyl quinic acid Thearubigins represented an estimated 75-82% of the total phenolics Further, polyphenol fractions were in decreasing order theaflavins, flavan-3-ols, flavonols, gallic acids and hydroxycinnamates On average, a cup of a consumer brew of black tea is providing polyphenols at the level of 262mg GAE/serving, of which 65 mg were assigned to individual polyphenols The antioxidant activity of black tea preparations is higher than that of most reported dietary agents on a daily basis Correlations were observed between the antioxidant activities and the sum of all quantified polyphenols by HPLC analysis as well as with the total phenolics Treatment of the black tea brew with simulated gastric juice resulted in a significant increase of the identified theaflavins implying a partial cleavage of thearubigins in the environment of the gastric lumen Therefore, black tea can be considered to be a rich source of polyphenols and/or antioxidants

Abstract: Dietary fibre, total polyphenols and phenolic acids in Spanish apples, peaches and pears were analysed and compared with their total radical-trapping antioxidative potential (TRAP). There were no significant differences in the content of dietary fibre among the studied fruits. The content of total polyphenols was 2.4 � 0.4, 2.1 � 0.3 and 6.9 � 0.7g kg � 1 in peeled fruits and 4.7 � 0.4, 4.5 � 0.4 and 11.1 � 1.2g kg � 1 in their peels for peaches, pears and apples respectively. The contents of dietary fibre, total polyphenols, caffeic, p-coumaric and ferulic acids and the TRAP values were significantly (P <0.05) higher in peels than in peeled fruits. The contents of all studied compounds and the TRAP values were significantly higher in peeled apples and their peel than in peaches and pears. We observed a strong correlation between the contents of total polyphenols and phenolic acids and the total radical- trapping antioxidative potential in all three fruits. The relatively high content of dietary fibre, the highest contents of total polyphenols, caffeic, p-coumaric and ferulic acids and the highest value of TRAP make apples preferable among the studied fruits for dietary prevention of atherosclerosis and other diseases. # 2002 Society of Chemical Industry

Abstract: The effect of natural phenolic compounds on the antioxidant and prooxidant activity of lactoferrin was studied in liposomes and oil-in-water emulsions containing iron. The antioxidants tested with lactoferrin were alpha-tocopherol, ferulic acid, coumaric acid, tyrosol, and natural phenolic extracts obtained from three different extra-virgin olive oils and olive mill wastewater. The natural extracts of olive oils and mill wastewaters were composed mainly of polyphenols and simple phenolics, respectively. Lipid oxidation at 30 degrees C was determined by the formation of hydroperoxides and fluorescent compounds resulting from oxidized lipid interactions. All phenolic compounds showed synergistic properties in reinforcing the antioxidant activity of lactoferrin in lipid systems containing iron. The highest synergistic effects were observed for the phenolic extracts rich in polyphenols of extra-virgin olive oils and lactoferrin. This synergistic effect was higher in liposomes than in emulsions.

Abstract: Background: There has been growing interest in the analysis of certain polyphenols in wine, especially flavonoids, trihydroxystilbenes and phenolic acids, stimulated by intense research into their potential benefits to human health. One of their main properties in this regard is their antioxidant activity, which enables them to attenuate the development of atherosclerosis, inflammatory diseases, and cancer. Methods: A two stage CD-1 mouse skin cancer model using 9,10-dimethyl-1,2-benzanthracene (DMBA) as initiator and phorbol 12-myristate 13-acetate (TPA) as promoter was employed to compare the antitumorigenic activities of one polyphenol from each of four different classes: flavanols [()-catechin], stilbenes ( trans-resveratrol), flavonols (quercetin) and hydroxybenzoic acids (gallic acid). Animals were treated with specific polyphenols at doses ranging from 0 to 25 moles (dissolved in 200 L acetone), twice a week for eighteen weeks. The solution was applied topically to the shaved dorsal region of each animal. The relative potencies of the polyphenols were compared by evaluating the percentage inhibition of tumor formation in individual mice and the number of mice developing one or more tumors with the different dose schedules. Results: Probit analysis revealed that quercetin was the most (ED 501 mole) and gallic acid the least effective (ED50 5‐10moles). ()-Catechin and trans-resveratrol were intermediate, with ED50 values of 5 and 6 moles, respectively. Conclusion: We have shown recently that trans-resveratrol is absorbed much more efficiently than ()-catechin and quercetin in humans after oral consumption. Taking this and the relative concentrations in red wine into account, together with the present results, we conclude that trans-resveratrol may be the most effective anticancer polyphenol present in red wine as consumed po by healthy human subjects.

Abstract: Unfermented and partly fermented dried cocoa beans have an excessively astringent and bitter flavour owing to their high polyphenol content. Studies on the remaining polyphenol oxidase activity and the oxidation of polyphenols in these beans have been conducted in relation to two factors, ie incubation time (0, 1, 2, 4, 8 and 16h) and pH of incubation (3.5, 4.5, 5.5 and 6.5). Owing to unsuccessful polyphenol oxidation during incubation of partly fermented beans, incubation-enrichment treatments were carried out by combining incubation time (0, 8, 16, 24 and 32 h) and addition of crude cocoa polyphenol oxidase and purified tyrosinase from mushroom at 88 and 8800 units g -1 and pH 5.5. Results showed that the remaining polyphenol oxidase activities of unfermented and partly fermented dried beans were 1 and 0.08% with specific activities of 9 and 1% respectively. The polyphenols of unfermented beans were effectively oxidised by incubation at 45 °C and pH 3.5-6.5 without enzyme enrichment; while those of partly fermented beans required enzyme enrichment. Both crude cocoa polyphenol oxidase and tyrosinase could be used for enzyme enrichment, but tyrosinase seemed to be more effective. Les feves de cacao non fermentees ou partiellement fermentees ont une flaveur tres astringente et amere due a leur teneur elevee en polyphenols. Cette etude evalue l'oxydation des polyphenols dans ces feves par une incubation de polyphenol oxydase (PPO) extraite de feves de cacao lyophilisees et une tyrosinase commerciale purifiee de champignon. Les resultats montrent que la PPO du cacao et la tyrosinase peuvent etre utilisees pour un enrichissement enzymatique mais la tyrosinase semble la plus efficace.

Abstract: There are literally thousands of known agents with potential chemopreventive and antioxidant activity; however, the expanding list of natural and synthetic compounds makes it difficult to test every agent in the widely accepted 2-year animal bioassay and human clinical trials. Therefore, short-term screening assays are needed to sort out the most efficacious compounds for long-term animal studies. In the present study, the identification of chemopreventive agents with efficacious antioxidant potential was explored with a Cu2+-mediated Fenton-type reaction, coupled with oxidative DNA lesion detection by 32P-postlabeling. Several agents inhibited the formation of 8-oxo-2'-deoxyguanosine (8-oxodG), a benchmark oxidative DNA lesion, but ellagic acid, a polyphenol found in berries, offered maximal (>80%) inhibition of 8-oxodG formation. However, a well-known tea polyphenol, epigallocatechin gallate, along with silymarin and D,L-sulforaphane, exhibited a pro-oxidant effect, with 50-70% increase in 8-oxodG induction. In general, our results agree with the reported antioxidant - pro-oxidant activities of the compounds, rendering this in vitro screening assay to be useful in determining the antioxidant potential of compounds rapidly and cost-effectively.

Abstract: 1. Free Radicals in Food: Introduction FOOD CHEMISTRY 2. EPR Methods for Studying Free Radicals in Foods 3. Free Radical Generation during Extrusion: A Critical Contributor to Texturization 4. Crosspy - A Radical Intermediate of Melanoidin Formation in Roasted Coffee 5. Radical Induced Formation of D-Glucosone from Amadori Compounds 6. Factors Influencing Free Radical Generation in Food Emulsions 7. Spin Label Study of Water Binding and Protein Mobility in Lysozyme 8. Radical Formation in Dairy Products: Prediction of Oxidative Stability based on Electron Spin Resonance Spectroscopy 9. The Influence of Ascorbic Acid and Uric Acid on the Oxidative Stability of Raw and Pasteurized Milk from dehydrascorbic acid in bovine milk 10. Pseudoperoxidase Activity of Myoglobin: Pigment Catalyzed Formation of Radicals in Meat Systems 11. NO Production during Thermal Processing of Beef: Evidence for Protein Oxidation ANTIOXIDANTS 12. Antioxidants in Plants and Oleaginous Seeds 13. Inhibition of Citral Deterioration 14. Antioxidant Activity of Tannins and Tannin-Protein Complexes 15. Effect of Roasting Process on the Antioxidant Properties Cassia tora L. 16. Free Radical and Oxidative Reactions of (-)-Epigallocatechin and (-)-Epigallocatechin Gallate, Two major Polyphenols in Green Tea 17. Radical-Scavenging Activity of Green Tea Polyphenols 18. Protective effect of phytic acid and its hydrolysis products on iron ion-induced oxidative damage in the large intestinal mucosa: In vitro and ex vivo study 19. Bromination, Chlorination and Nitration of Isoflavonoids NUTRITIONAL BIOCHEMISTRY AND HEALTH 20. Inhibition of Xanthine Oxidase and NADPH Oxidase by Tea Polyphenols 21. Generation of lipid peroxyl radicals from oxidized edible oils and heme-iron: Implication of a high-fat diet in colon carcinogenesis 22. Wasabi: A Traditional Japanese Food that Containing on Exceedingly Potent Glutathione S-Transferase Inducer for RL34 Cells 23. Antioxidants and Anti-atherosclerotic Effects of Chinese Medicinal Herb Salvia Miltiorrhiza 24. Suppressive Effects of 1'-Acetoxychavicol Acetate on Superoxide and Nitric oxide in Cell Culture systems, and on Hydrogen Peroxide in Mouse Skin

Abstract: Chlorogenic acid is the major polyphenol in foods derived from plants and is a good substrate for polyphenol oxidase. Chlorogenic acid quinone (CQA-Q), which is an oxidative product of chlorogenic acid by polyphenol oxidase, is an important intermediate compound in enzymatic browning. CQA-Q was prepared, and its properties and the relationship with browning were examined. The quinone solution was yellow or orange, and its molecular absorption coefficient was estimated to be 1.7 x 10(3) for 325 nm and 9.7 x 10(2) for 400 nm in an acidic aqueous solution. Chlorogenic acid and H2O2 were spontaneously generated in the CQA-Q solution as the yellowish color of the solution gradually faded. A pale colored polymer was the major product in the reaction solution. Amino acids such as lysine and arginine added to CQA-Q solution did not repress the fading of the yellowish color of the solution. We concluded from these results that CQA-Q itself and a mixture of CQA-Q and amino acids did not form intensive brown pigments in the acidic aqueous solution. H2O2 spontaneously formed in the CQA-Q solution, and other polyphenols might have played an important role in the formation of the brown color by enzymatic browning.