Inhibition of eleven mutagens by various tea extracts, (-)epigallocatechin-3-gallate, gallic acid and caffeine

The antimutagenic properties of various tea extracts (green tea, pauchong t ea, oolong tea and black tea) and their components including (-)-epigalloca techin-3-gallate (EGCG), gallic acid and caffeine were examined by the Ames test. The antimutagenic activity of the green tea extract against N-methyl -N'-nitro-N-nitrosoguanidine (MNNG), folpet and monocrotophos was greater t han those of pouchong, oolong and black tea extracts. The antimutagenic eff ects of tea extracts against 2-acetylaminofluorene (AAF) decreased as follo ws: oolong tea > pauchong tea > black tea > green tea. Furthermore, black t ea showed a greater antimutagenic activity against benzo[a]pyrene (BP). The pauchong tea showed a stronger inhibitory effect against 9-aminoacridine ( 9AA) and aflatoxin B-1 (AFB(1)) than other tea extracts. EGCG markedly supp ressed the direct-acting mutagenicity of MNNG, N-nitroso-N-methylurea (MNU) , captan, and folpet which were alkylating agents and fungicides. Similarly , gallic acid, the major component of black tea strongly inhibited the muta genicity of 9AA, and moderately inhibited the mutagenicity of MNNG and folp et. The caffeine was less active. EGCG and gallic acid perhaps could act as nucleophiles to scavenge the electrophilic mutagens. Taken together, these results suggest that formation of different metabolites during various sta ges of tea fermentation may affect antimutagenic potencies against differen t types of chemical mutagens. (C) 1999 Elsevier Science Ltd. All rights res erved.