CHEMOPREVENTIVE POTENTIAL OF DIETARY BIOFLAVONOIDS AGAINST 20-METHYLCHOLANTHRENE-INDUCED TUMORIGENESIS

The effect of dietary supplementation of flavonoidal compounds such as quercetin, rutin, luteolin and (+)-catechin on the incidence of fibro sarcoma induced by 20-methylcholanthrene (20-MC) in male Swiss albino mice was observed. Subcutaneous injection of 20-MC produced 100% tumor incidence and the onset of tumor appeared within 7 weeks, while flavo noid-treated mice (1% quercetin- and luteolin-mixed diets) produced tu mors in the 9th week, and the tumor incidences in mice treated with qu ercetin- and luteolin-mixed diets were 52% and 60%, respectively. Subc utaneous administration of 20-MC along with the flavonoidal compounds (quercetin, luteolin) was found to have significant effect on tumor ex pression. The compounds rutin and (+)-catechin did not influence tumor expression in both experiments. Elevated levels of lipid peroxides, c ytochrome P450 and decreased activity of glutathione-S-transferase (GS T) were observed in the tumor bearing animals. Test-diet-treated anima ls showed reduction in the lipid peroxides and cytochrome P450, and in creased activity of GST (P < 0.001). In vitro [H-3]thymidine incorpora tion showed the inhibition of DNA synthesis in fibrosarcoma cells by t he flavonoids. The possible mode of action of the flavonoidal compound s may be through their influence on the initiation and promotion phase s of the carcinogenic process coupled with enhancement of the detoxifi cation process.