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Mutagenesis vol. 13 no. 6 pp. 631-636, 1998
© 1998 UK Environmental Mutagen Society/Oxford University Press

research-article

Contribution of theafulvins to the antimutagenicity of black tea: their mechanism of action

Fenton Catteral, Emma Copeland, Michael N. Clifford and Costas Ioannides1

School of Biological Sciences, University of Surrey Guildford, Surrey GU2 5XH, UK

Theafulvins were isolated from black tea aqueous infusions and their antimutagenic activity was evaluated against a number of food carcinogens. Theafulvins gave rise to a concentration-dependent inhibition of the mutagenicity of 2-amino-3-methylimidazo-[4,5-f]quinoline, 2-amino-lmethyI-6-phenylimidazo[4,5-b]pyridine, benzo[a]pyrene,7,12-dimethylbenz[a]anthracene, nitrosopyrrolidine and nitrosopiperidine, but, in contrast, the mutagenicity of aflatoxin B1 was enhanced. The mutagenicity exhibited by N'-methyl-N'-nitro-N-nitrosoguanidine and 9-aminoacridine was not influenced and weakly inhibited by theafulvins, respectively. 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 metabolism was terminated after metabolic activation of the promutagens, incorporation of the theafulvins into the activation system did not modulate the mutagenic response. It is concluded that theafulvins play an important role in the antimutagenic activity of black tea by inhibiting cytochrome P450-dependent bioactivation of the carcinogens.

1To whom correspondence should be addressed. Tel: +44 1483 259709; Fax: +44 1483 576978; Email: c.ioannides{at}surrey.ac.uk


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