Epigallocatechin activity

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. 

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. 

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]. 

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

Ahn, S.C. et al., Epigallocatechin-3-gallate, constituent of green tea, suppresses the LPS-induced phenotypic and functional maturation of murine dendritic cells through inhibition of mitogen-activated protein kinases and NF-kappaB, Biochem Biophys Res Commun, 313, 148, 2004. 

Lin, Y.L. and Lin, J.K., (-)-Epigallocatechin-3-gallate blocks the induction of nitric oxide synthase by down-regulating lipopolysaccharide-induced activity of transcription factor nuclear factor-kappaB, Mol Pharmacol, 52, 465, 1997. 

Antiviral activity. Epigallocatechin-3-gal-late, administered to Hep2 cells in culture, produced a therapeutic index of 22 and an ICjf, of 25 pM. The agent was the most effective when added to the cells during the transition from the early to the late phase of viral infection suggesting that the polyphenol inhibits one or more late steps in virus infection " . 

Lorenz, M., Wessler, S., Follmann, E., Michaelis, W., Dusterhoft, T., Baumann, G., Stangl, K, and Stangl, V., A constituent of green tea, epigallocatechin-3-gallate, activates rndothelial nitric oxide synthase by a phosphatidylinositol-3-OH-kinase-, cAMP-dependent protein kinase-, and Akt-dependent pathway and leads to endothelial-dependent vasorelaxation, J. Biol Chem., 279, 6190, 2004. 

Coetzee, J. et al., Oligomeric flavanoids. Part 31. Structure and synthesis of the first procassinidin dimers based on epicatechin, and gallo- and epigallocatechin. Phytochemistry, 53, 795, 2000. Hatano, T. et al., Flavan dimers with lipase inhibitory activity from Cassia nomame. Phytochemistry, 46, 893, 1997. 

Dong, Z., Ma, W.-Y., Huang, C.,Yang, C. S., 1997, Inhibition of tumor promoter induced activator protein 1 activation and cell transformation by tea polyphenols, (-)-epigallocatechin gallate and theaflavins, Cancer Res. 57 4414-4419. 

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