Epigallocatechin 3-gallate

Chemical Antioxidant Systems. The antioxidant activity of tea extracts and tea polyphenols have been determined using in vitro model systems which are based on hydroxyl-, peroxyl-, superoxide-, hydrogen peroxide-, and oxygen-induced oxidation reactions (109—113). The effectiveness of purified tea polyphenols and cmde tea extracts as antioxidants against the autoxidation of fats has been studied using the standard Rancimat system, an assay based on air oxidation of fats or oils. A direct correlation between the antioxidant index of a tea extract and the concentration of epigallocatechin gallate in the extract was found (107). 

The total antioxidant activity of teas and tea polyphenols in aqueous phase oxidation reactions has been deterrnined using an assay based on oxidation of 2,2 -azinobis-(3-ethylbenzothiazoline-sulfonate) (ABTS) by peroxyl radicals (114—117). Black and green tea extracts (2500 ppm) were found to be 8—12 times more effective antioxidants than a 1-mAf solution of the water-soluble form of vitamin E, Trolox. The most potent antioxidants of the tea flavonoids were found to be epicatechin gallate and epigallocatechin gallate. A 1-mAf solution of these flavanols were found respectively to be 4.9 and 4.8 times more potent than a 1-mAf solution of Trolox in scavenging an ABT radical cation. 

HU G, HAN c and chen j (1995) Inhibition of oncogene expression by green tea and (-)-epigallocatechin gallate in mice Nutrition and Cancer 24, 203-9. 

COPLAND E L, CLIFFORD M N and WILLIAMS c M (1998) Preparation of (-)-epigallocatechin gallate from commercial green tea by caffeine precipitation and solvent partition . Food Chem, 61, 81-7. 

D s (1996) Prevention of photocarcinogenesis by topical administration of pure epigallocatechin gallate isolated from green tea , Nutr Cancer, 26 (3), 325-35. 

KATIYAR s K, MATSUI M s, ELMETS c A and MUKHTAR H (1999) Polyphenolic antioxidant epigallocatechin gallate from green tea reduces UVB-induced inflammatory responses and infiltration of leukocytes in human skin , Photochem Photobiol, 69, 148-53. 

KHAFIF A, SCHANTZ s P, CHOU T c, EDELSTEIN D and SACKS P G (1998) Quantitation of chemopreventive synergism between epigallocatechin gallate and curcumin in normal, premalignant, and malignant oral epithelial cells . Carcinogenesis, 19, 419-24. 

LONG L H, CLEMENT M V and HALLiwELL B (2000) Artifacts in cell-culture rapid generation of hydrogen peroxide on addition of (-)-epigaUocatechin, (-)-epigallocatechin gallate, (-i-)-catechin, and quercetin , Biochem Biophys Res Commun, 273 (1), 50-53. 

SUGANUMA M, OKABE s, KAi Y, suEOKA N, suEOKA E and FUJiKi H (1999) Synergistic effects of (-)-epigallocatechin gallate with (-)-epicatechin, sulindac, or tamoxifen on cancer-preventive activity in human lung cancer cell line PC-9 , Cancer Res, 59, 44-7. 

UNNO T, KONDO K, iTAKURA H and TAKEO T (1996) Analysis of (-)-epigallocatechin gallate in hiunan serum obtained after ingesting green tea , Biosci Biotech Biochem, 60, 2066-68. 

The catechins are soluble in water, colorless, and possess an astringent taste. They are easily oxidized and form complexes with many other substances including the methylxanthines.44 Epigallocatechin gallate is the... 

Bisflavanols are the compounds formed by the coupling of the quino-nes produced by the oxidation of epigallocatechin and epigallocatechin gallate.50 The three predicted bisflavanols have been found and characterized in black tea. They are illustrated in Figure 5. They occur only in very small quantities in black tea, presumably because of high reactivity. Re-... 

Hayakawa S, Saeki K, Sazuka M, et al. Apoptosis induction by epigallocatechin gallate involves its binding to Fas. Biochem Biophys Res Commun 2001 285 1102-1106. 

Figure 5.3. Flavanol monomers (catechins, epicatechins, and their gallates) and pro-cyanidins. C catechin GC, gallocatechin EC, epicatechin EGC, epigallocatechin CG, catechin gallate GCG, gallocatechin gallate ECG, epicatechin gallate, EGCG, epigallocatechin gallate.

Chen JJ, Ye ZQ and Koo MW. 2004. Growth inhibition and cell cycle arrest effects of epigallocatechin gallate in the NBT-II bladder tumour cell line. BJU Int 93(7) 1082-1086. 

Classic antioxidants, vitamin E, vitamin C, and others can suppress the activation of apoptosis. For example, ascorbic acid prevented cytochrome c release and caspase activation in human leukemia cells exposed to hydrogen peroxide [128], Pretreatment with A -acctylcystcinc, ascorbate, and vitamin E decreased homocysteine thiolactone-induced apoptosis in human promyelocytic leukemia HL-60 cells [129]. Resveratrol protected rat brain mitochondria from anoxia-reoxygenation damage by the inhibition of cytochrome c release and the reduction of superoxide production [130]. However, it should be mentioned that the proapoptotic effect of ascorbate, gallic acid, or epigallocatechin gallate has been shown in the same human promyelocytic leukemia cells [131]. 

Chow, H.H. et al., Pharmacokinetics and safety of green tea polyphenols after multiple-dose administration of epigallocatechin gallate and polyphenon E in healthy individuals, Clin Cancer Res, 9, 3312, 2003. 

Zenda, N. et al., Erythrocyte-dependent mitogenic activity of epigallocatechin gallate on mouse splenic B cells, Int J Immunopharmacol, 19, 399, 1997. 

Rogers, J. et al., Epigallocatechin Gallate Modulates Cytokine Production by Bone Marrow-Derived Dendritic Cells Stimulated with Lipopolysaccharide or Muramyldipeptide, or Infected with Legionella pneumophila, Exp Biol Med (Maywood), 230, 645, 2005. 

Nakagawa, H. etal., Generation of hydrogen peroxide primarily contributes to the induction of Fe(II)-dependent apoptosis in Jurkat cells by (-)-epigallocatechin gallate, Carcinogenesis, 25, 1567, 2004. 

Kawai, K. et al., Epigallocatechin gallate attenuates adhesion and migration of CD8+ T cells by binding to CDllb, J Allergy Clin Immunol, 113, 1211, 2004. 

Fig. 1. Amperometric monitoring of the autoxidation of epigallocatechin gallete in the presence of (A) 0, (B) 2.0, (C) 5.0, (D) 10, (E) 20, and (F) 50 pm CuCl2. The measurements were performed in 0.1 M Tris buffer (pH 9.0) with a Clark type oxygen electrode at 28 °C. The epigallocatechin gallate concentration was fixed at 50 pm. The catechin stock solution was injected into the test solution at t = 0. The inset shows the (initial) steady-state autoxidation rate as a function of Cu2+ concentration. Reprinted from Biochimica et Biophysica Acta, vol. 1569, Mochizuki, M. Yamazaki, S. Kano, K. Ikeda,T., Kinetic analysis and mechanistic aspects of autoxidation of catechins, p. 35, Copyright (2002), with permission from Elsevier Science.

Fig. 2.62. HPLC chromatogram of (a) jasmin (green) tea, (b) Fujian Oolong tea, (c) pu-erh tea and (d) black tea at 280 nm. Peak identification 1 = gallic acid (GA) 2 = (-)-epigallocatechin (EGC) 3 = (-)-epigallocatechin gallate (EGCG) 4 = epicatechin (EC) 5 = (-)-epicatechin gallate (ECG) 6 = caffeine (CA) 7 = ( — )-catechin gallate (CG). Reprinted with permission from Y. Zuo et al. [178].

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