INHIBITION BY AN EXTRACT OF OCIMUM-SANCTUM OF DNA-BINDING ACTIVITY OF7,12-DIMETHYLBENZ[A]ANTHRACENE IN RAT HEPATOCYTES IN-VITRO

Ocimnm snnctnm is a traditional medicinal plant. Previous studies have shown that extracts of O. sanctum inhibit the induction of skin papil lomas in mice by 7,12-dimethylbenz[a]anthracene (DMBA). In the present study, primary cultures of rat hepatocytes were treated with 0-500 mu g of O. sanctum extract for 24 h and then with DMBA (10 or 50 mu g) f or 18 h. Cells were then harvested and their DNA was isolated and anal yzed by P-32-postlabelling. A significant reduction in the levels of D MBA-DNA adducts was observed in all cultures pretreated with O. sanctu m extract. This effect was more pronounced at the lower dose of DMBA ( 10 mu g). Hepatocytes which were treated with the highest dose of extr act (500 mu g) showed a maximum reduction of 93% in the mean values of DMBA-DNA adducts. The viability of the cells was not adversely affect ed by pretreatment with extract. Our findings suggest that O. sanctum leaf extract blocks or suppresses the events associated with chemical carcinogenesis by inhibiting metabolic activation of the carcinogen. ( C) 1998 Elsevier Science Ireland Ltd. All rights reserved.