Protection against benzo[<i>α</i>]pyrene- and <i>N</i>-nitrosodiethylamineinduced lung and forestomach tumorigenesis in A/J mice by water extracts of green tea and licorice

Abstract

Next to water, tea is the most widely consumed beverage in the world. Licorice, a traditional herb, is used as a food sweetening and flavoring agent worldwide. Previously we have shown that the polyphenolic fraction isolated from green tea (GTP*) and constituents derived from licorice possess significant antimutagenic activity and afford protection against carcinogenesis in murine skin. In this study we observed that oral feeding in drinking water of 1.2% water extract of green tea (WEGT) or 1 % water extract of licorice (WEL) to female A/J mice during the entire period of the experiment results in significant protection against lung and forestomach tumorigenesis induced by benzo[a]pyrene (B[a]P) (p.o., 100 mg/kg body wt total four times at 2 week intervals) or N-nitrosodiethylamine (NDEA) (p.o., 20 mg/kg body wt, once weekly for 8 weeks). At the termination of the experiment at 33 weeks post B[a]P and NDEA administration, the animals receiving WEGT developed respectively 56 and 55% (P < 0.05) fewer tumors in lungs than did controls receiving normal drinking water. WEGT feeding also reduced these two carcinogen-induced tumor yields in forestomach by 71 and 80% (P < 0.05) respectively, as compared to that in animals receiving normal drinking water. Similarly, the animals receiving WEL developed 60 and 55% and 24 and 68% (P < 0.05, except for 24% protective effect) fewer tumors than did controls receiving normal drinking water. The results of the present study, in conjunction with prior publications, suggest that green tea and licorice possess cancer chemopreventive effects against various carcinogens in different animal tumor bioassay protocols.