ANTIMUTAGENIC ACTIVITY OF TEA TOWARDS 2-HYDROXYAMINO-3-METHYLIMIDAZO[4,5-F]QUINOLINE - EFFECT OF TEA CONCENTRATION AND BREW TIME ON ELECTROPHILE SCAVENGING

Green tea and black tea inhibit colon carcinogenesis in rats exposed t o the cooked meat-derived mutagen 2-amino-3-methylimidazo[4,5-f]quinol ine (IQ). The present study compared the inhibitory activities of gree n tea and black tea towards a direct-acting mutagenic metabolite of IQ , namely 2-hydroxyamino-3-methylimidazo[4,5-f]quinoline (N-hydroxy-IQ) , under various brewing conditions. The following observations were ma de: (a) green tea (Sencha midoriiro) and black tea (English Breakfast tea) brewed at concentrations of 1.25%, 2.5% or 5.0% (w/v) dose-relate dly inhibited the mutagenic activity of N-hydroxy-IQ in the Salmonella assay, (b) most of the antimutagenic components were released from th e teas within 1-2 min of brewing, (c) under identical brewing conditio ns, green tea was significantly more effective than black tea, and (d) fractionation of green tea by HPLC revealed that most of the antimuta genic activity co-eluted with the compounds epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG), both of which are known for their anti-oxidant properties. These results suggest that catechins in tea m ight protect against such diverse reactive intermediates as free radic als and electrophiles formed during the metabolic activation of carcin ogens and mutagens. (C) 1998 Elsevier Science B.V. All rights reserved .