Evaluation of therapeutic effect of omega-6 linoleic acid and thymoquinone enriched extracts from Nigella sativa oil in the mitigation of lipidemic oxidative stress in rats

Objective: Nigella sativa belongs to the Ranunculaceae family. The therapeutic role of methanolic extract (ME) and volatile oil (VO) fractionated from N. sativa seed oil was investigated for antiperoxidative and antioxidant effects in atherogenic suspension fed rats.

Methods: We examined the protective effects of ME and VO on the enzymatic and nonenzymatic antioxidants status in erythrocytes and the livers of atherogenic suspension fed rats. As a marker of lipid peroxidation, we estimated the conjugated diene, lipid hydroperoxide, and malondialdehyde concentrations in plasma in the following groups of rats: normolipidemic control, hyperlipidemic control, hyperlipidemic methanolic extract, and hyperlipidemic volatile oil. ME 500 mg or VO 100 mg/kg body weight of male rat was orally administrated for 30 d.

Results: Pretreatment of hyperlipidemic rats with these test extracts resulted in a significant decrease (P < 0.001) in the level of lipid peroxidation markers, conjugated diene, lipid hydroperoxide, and malondialdehyde (16-50%) compared to the hyperlipidemic control rats. In addition, ME and VO significantly (P < 0.001) elevated the hepatic and erythrocyte superoxide dismutase, catalase, and glutathione reductase activities (19-58%) compared to the hyperlipidemic rats. In liver homogenate of hyperlipidemic-ME and hyperlipidemic-VO, the glutathione-S-transferase activity was protected by 93% and 89%, and in erythrocytes, the glutathione peroxidase activity was protected by 90% and 77%, respectively. Interestingly, reduced glutathione level and activities of ATPases were protected to near normal levels. Pretreatment of rats with the test extracts replenished effectively (P < 0.001) the plasma total antioxidant power by an average of 88% against free radicals.

Conclusions: The lipidemic oxidative stress was effectively mitigated by antiperoxidative activities of ME and VO. Thus, these test extracts, especially ME, may be used as antioxidant as well as hypolipidemic agents in the form of natural food supplement to prevent or treat diseases caused by free radicals.