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.