Catechins are not major components responsible for anti-genotoxic effects of tea extracts against nitroarenes

The anti-genotoxic properties of tea leaf extracts were examined in a Salmo nella umu-test. Seven non-fermented teas (green tea), one semi-fermented te a (oolong tea), two fermented teas (black tea and Chinese pu er tea) and tw o other teas were examined for their anti-genotoxic abilities and for their catechins contents. This was to study the relationship between catechins c ontents and anti-genotoxic activity of various tea leaf extracts. All types of tea extracts showed more potent suppressive effects against umu gene ex pression of the SOS response in Salmonella typhimurium TA1535/pSK 1002 indu ced by four nitroarenes (1-nitropyrene, 2-nitrofluorene, 3-nitrofluoranthen e and a mixture of 1,6- and 1,8-dinitropyrene) rather than 4-NQO, AF-2 and MNNG. The anti-genotoxic effect of 12 tea leaf extracts on 1-NP, 2-NF, 3-NF and DNP decreased in the order: oolong tea (semi-fermented tea) > black te a (fermented tea) > sencha (non-fermented tea, an ordinary grade green tea) > tocyucya (other tea) > Chinese pu er tea (fermented tea). The amount of catechins (EGC, C, EGCG, EC and ECG) in various teas in decreasing order wa s non-fermented tea > semi-fermented tea > fermented tea > other tea. A rem arkable feature was the effectiveness of black tea and Chinese pu er tea in suppressing the genotoxicity induced by nitroarenes, in spite of the fact that these fermented teas do not have high catechins contents. Statistical analysis showed that no significant (P < 0.01) correlation was found betwee n the anti-genotoxicity of tea extracts against nitroarenes and the catechi ns contents in tea leaf extracts. In further experiment, fractionation of s encha extract by HPLC revealed that anti-genotoxicity of the peak fraction corresponding to catechins accounted for < 10% of the total anti-genotoxic activity of sencha extract against for 1-nitropyrene. These results suggest that catechins are not major components responsible for the anti-genotoxic effects of tea leaf extracts against direct-acting nitroarenes. (C) 2001 E lsevier Science B.V. All rights reserved.