Thymoquinone is a potent superoxide anion scavenger
The antioxidant and pro-oxidant effects of thymoquinone (TQ), a natural main constituent of the volatile oil of Nigella sativa seeds, and a synthetic structurallyrelated tert-butylhydroquinone (TBHQ), were examined in vitro. Both TQ and TBHQ efficiently inhibited iron-dependent microsomal lipid peroxidation in a concentration-dependent manner with median inhibitory concentration (IC50) values of 16.8 and 14.9 μM, respectively. TBHQ was stronger than TQ as a scavenger of 2,2′-diphenyl-p-picrylhydrazyl radical (DPPH) (IC50 = 5 μM, 200 times more active than TQ) and as a scavenger of hydroxyl radical (OH.) with an IC50 of 4.6 μM (approximately 10 times more active than TQ). TQ was more active than TBHQ as a superoxide anion scavenger with IC50 of 3.35 μM compared to 18.1 μM for TBHQ. Only TBHQ significantly promoted DNA damage in the bleomycin-Fe(III) system. The results suggest that both TQ and TBHQ have strong antioxidant potentials through scavenging ability of different free radicals. Moreover, the data indicate that TQ is acting mainly as a potent superoxide anion scavenger.
Badary, Osama A.; Taha, Ragia A.; Gamal El-Din, Ayman M.; and Abdel-Wahab, Mohamed H., "Thymoquinone is a potent superoxide anion scavenger" (2003). Pharmacy. 159.