STUDIES ON THE CHEMOPREVENTIVE POTENTIAL OF SOME NATURALLY-OCCURRING BIOFLAVONOIDS IN 7,12-DIMETHYLBENZ(A)ANTHRACENE-INDUCED CARCINOGENESISIN MOUSE SKIN

The chemopreventive action of four dietary flavonoidal compounds, quer cetin, rutin, luteolin, and (+)catechin, on 7,12-dimethylbenz(a)anthra cene (DMBA)-induced skin carcinogenesis was studied in male Swiss albi no mice. Topical application of DMBA (0.24%) as initiator for 2 weeks and croton oil as promoter for 4 weeks produced 100% incidence of skin tumor in control animals. Prior topical treatment with quercetin or l uteolin reduced the mean papilloma formation, while rutin and (+)catec hin were found to exert a minimal effect against DMBA-induced papillom a formation. By continuous application of flavonoidal compound along w ith initiator and promoter, the papilloma incidence was found to be 32 % for quercetin, 40% for luteolin, 58% for rutin, and 71% for (+)catec hin. The mean number of papillomas per mouse was found to be 2.52 in t he DMBA control, whereas it was significantly decreased in quercetin ( 0.45, p<0.001)-, luteolin (0.52, p< 0.001)-, rutin (1.58, p<0.05)-, an d (+)catechin (1.67, p<0.05)-treated mice. Increased levels of glutath ione and glutathione-S-transferase and decreased levels of lipid perox ides and cytochrome P-450 were observed when the flavonoid treatment w as given along with the DMBA. The possible mode of action of the flavo noidal compounds may be their influence on the activating enzymes of t he carcinogens in mouse skin.