FRACTIONATION OF GREEN TEA EXTRACTS - CORRELATION OF ANTIMUTAGENIC EFFECT WITH FLAVANOL CONTENT

The present study was undertaken to evaluate the role of individual fl avanols in the antimutagenic potential of green tea. Aqueous extracts of green tea were fractionated into four fractions, each of which was fully defined with respect to its content of (-)-epigallocatechin gall ate, (-)-epicatechin gallate, (-)-epigallocatechin, (-)-epicatechin an d gallic acid. The ability of each fraction to antagonize the mutageni city of four model mutagens, namely N-nitrosopyrrolidine, benzo(a)pyre ne, 2-aminoanthracene and Glu-P-1 (2-amino-6-methyldipyrido[1,2-a : 3, 2-d]imidazole), was investigated in the Ames test. No correlation coul d be established between any of the flavanols and antimutagenic potent ial. Similarly, no correlation was evident between the flavanol conten t of each fraction and its ability to inhibit CYP1A, as exemplified by the O-dealkylations of methoxy-and ethoxy-resorufin. Furthermore, no relationship could be established between CYP2B activity, as exemplifi ed by the O-depentylation of pentoxyresorufin and the antimutagenic po tential of green tea. Using a modified Ames test procedure, the abilit y of each tea fraction to scavenge the metabolically generated reactiv e intermediates of the model mutagens was investigated, this being an additional mechanism of the antimutagenic potential of green tea. Gene rally, fractions with high flavanol content were more effective scaven gers. It is concluded that the contribution of flavanols to the antimu tagenic activity of green tea is, at best, limited.