Green tea extracts

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. 

DETERMINATION OF POLYPHENOLIC ENANTIOMERS IN GREEN TEA EXTRACT BY CAPILLARY ZONE ELECTROPHORESIS... 

Catechin and epicatechin are two flavanols of the catechin family. They are enantiomers. The capillary zone electrophoresis (CE) methods with UV-detection were developed for quantitative determination of this flavanols in green tea extracts. For this purpose following conditions were varied mnning buffers, pH and concentration of chiral additive (P-cyclodextrin was chosen as a chiral selector). Borate buffers improve selectivity of separation because borate can make complexes with ortho-dihydroxy groups on the flavanoid nucleus. 

Many solid dosage forms made with green tea extracts can be seen in the market, and several are standardised to a content of polyphenols or catechins. 

J (1999) Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in hiunans , AmJ Clin Nutr, 70, 1040-45. 

SAKANAKA s, KIM M, TANiGUCHi M and YAMAMOTO T (1989) Antibacterial substances in Japanese green tea extract against Streptococcus mutans, a cariogenic bacterium , Agric Biol Chem, 53, 2307-11. 

HU M and SKIBSTED L H (2002b) Kinetics of reduction of ferryhnyoglohin by (-)-epigallocatetechin gallate and green tea extract, J Agric Food Chem, 50, 2998-3003. 

YOUNG J F, DRAGSTED L O, HARALDSDOTTIR J, DANESHVAR B, KALL M A, LOFT S, NILSSON L, NIELSEN S E, MAYER B, SKIBSTED L H, HUYNH-BA T, HERMETTER A and SANDSTROM B (2002) Green tea extract only affects markers of oxidative status postprandially lasting antioxidant effect of flavonoid-free diet, Brit J Nutr, 87, 343-55. 

In a similar way, several studies have been devoted to the study of antiprotozoal activity of catechins occurring in green tea extracts. The trypanocidal... 

Kavanagh KT, Hafer LJ, Kim DW, and others. 2001. Green tea extracts decrease carcinogen-induced mammary tumor burden in rats and rate of breast cancer cell proliferation in culture. J Cell Biochem 82(3) 387—398. 

Venables MC, Hulston CJ, Cox HR and Jeukendrup AE. 2008. Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans. Am J Clin Nutr 87(3) 778-784. 

Inagake M, Yamane T, Kitao Y, Oya K, Matsumoto H, Kikuoka N, Nakatani H, Takahashi T, Nishimura H and Iwashima A. 1995. Inhibition of 1,2-dimethylhydrazine-induced oxidative DNA damage by green tea extract in rat. Jpn J Cancer Res 86(11) 1106-1 111. 

Pearson DA, Frankel EN, Aeschbach R and German JB. 1998. Inhibition of endothelial cell mediated low-density lipoprotein oxidation by green tea extracts. J Agric Food Chem 46(4) 1445-1449. 

Unfortunately, to date, no formal clinical studies have been conducted to specifically evaluate the effects of green tea, green tea extracts, or EGCG on immune function. However, based on several Phase I studies that have evaluated EGCG and/or Polyphenon E (a defined, decaffeinated green tea polyphenol mixture) and found them to be safe and tolerable at relatively high doses, it is likely that future clinical studies may follow [66-69],... 

Pisters, K.M. et al., Phase I trial of oral green tea extract in adult patients with solid tumors, J Clin Oncol, 19, 1830, 2001. 

Matsubara S, Shibata H, Ishikawa F, Yokokura T, Takahashi M, Sugimura T, Wakabayashi K. (2003) Suppression of Helicobacter py/ori-induced gastritis by green tea extract in Mongolian gerbils. Biochem Biophys Res Commun 310 715-719. 

T. Nakatani, K. Ohtani, S. Sakanaka, CS059 M. Kim and I. Matsui-Yuasa. Protective effect of green tea extract and tea polyphenols against the cytotoxicity of 1,4-naphthoquinone in isolated rat hepatocytes. Biosci Biotech Biochem 1997 61(11) 1901-1905. 

CS160 Riso, P., D. Erba, F. Criscuoli and G. Testolin. Effect of green tea extract on DNA repair and oxidative damage due to H2O2 in Jurkat T cells. Nutrition Research 2002 22(10) 1143-1150. 

---