Abstract
The chemopreventive action of four dietary flavonoidal compounds, quercetin, rutin, luteolin, and (+)catechin, on 7, 12-dimethylbenz(a)anthracene (DMBA)-induced skin carcinogenesis was studied in male Swiss albino 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 luteolin reduced the mean papilloma formation, while rutin and (+)catechin were found to exert a minimal effect against DMBA-induced papilloma formation. By continuous application of flavonoidal compound along with initiator and promoter, the papilloma incidence was found to be 32% for quercetin, 40% for luteolin, 58% for rutin, and 71% for (+)catechin. The mean number of papillomas per mouse was found to be 2.52 in the 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)-, and (+)catechin (1.67, p<0.05)-treated mice. Increased levels of glutathione and glutathione-S-transferase and decreased levels of lipid peroxides and cytochrome P-450 were observed when the flavonoid treatment was given along with the DMBA. The possible mode of action of the flavonoidal compounds may be their influence on the activating enzymes of the carcinogens in mouse skin.
