CONTRIBUTION OF THEAFULVINS TO THE ANTIMUTAGENICITY OF BLACK TEA - THEIR MECHANISM OF ACTION

Theafulvins were isolated from black tea aqueous infusions and their a ntimutagenic activity was evaluated against a number of food carcinoge ns. Theafulvins gave rise to a concentration-dependent inhibition of t he mutagenicity of 2-amino-3-methylimidazo-[4,5-f]quinoline, 2-amino-1 -methyl-6-phenylimidazo[4,5-b]pyridine, benzo[a]pyrene, 7,12-dimethylb enz[a]anthracene, nitrosopyrrolidine and nitrosopiperidine, but, in co ntrast, the mutagenicity of aflatoxin B-1 was enhanced. The mutagenici ty exhibited by N'-methyl-N'-nitro-N-nitrosoguanidine and 9-aminoacrid ine was not influenced and weakly inhibited by theafulvins, respective ly. The p-hydroxylation of aniline and the O-dealkylations of methoxy- , ethoxy- and, to a lesser extent, pentoxyresorufin were inhibited by theafulvins in a concentration-dependent manner. When microsomal metab olism was terminated after metabolic activation of the promutagens, in corporation of the theafulvins into the activation system did not modu late the mutagenic response. It is concluded that theafulvins play an important role in the antimutagenic activity of black tea by inhibitin g cytochrome P450-dependent bioactivation of the carcinogens.