Inhibition of benzo(a)pyrene-induced forestomach carcinogenesis in mice bythymoquinone

The modulating effect of thymoquinone (TQ) on benzo(a)pyrene (BP)-induced f orestomach rumours was investigated in female Swiss albino mice, receiving oral administration of BP at a dose of 1 mg twice weekly for 4 weeks. Admin istration of 0.01% of TQ in drinking water 1 week before, during and after BP treatment until the end of the experiment resulted in significant suppre ssion of BP-induced tumourigenesis when compared with the group receiving B P alone, TQ inhibited both BP-induced forestomach tumour incidence and mult iplicity by 70% and 67%, respectively. Lipid peroxide accumulation and decr eased glutathione (GSH) content and glutathione-S-transferase (GST) and DT diaphorase activities were observed in the liver of BP-treated tumour-beari ng mice, TQ alone showed a significant induction in the enzyme activities o f hepatic GST and DT diaphorase, Mice treated with TQ along with BP showed almost normal hepatic lipid peroxides and GSH levels, and normal enzyme act ivities compared to the control group, The present data may indicate the po tential of TQ, the main constituent of the volatile oil of Nigella sativa s eed, as a powerful chemopreventive agent against BP-induced forestomach tum ours in mice. The possible modes of action of TQ may be through its antioxi dant and anti-inflammatory activities, coupled with enhancement of detoxifi cation processes, (C) 1999 Lippincott Williams & Wilkins.