ABSTRACT
Aim: In recent years, natural products from medicinal plants have received considerable attention. Thymoquinone, the major compound from Nigella sativa L. Is the most used due to its several pharmacological properties. This study was undertaken to evaluate the antioxidant effect of thymoquinone which is very useful in controlling free radicals noxious species causing the induction and / or amplification of a number of pathologies. Study Design: Spectrophotometric methods. Place and Duration of Study: Biochemistry Department, Applied Biochemistry Laboratory, Nature and Life Sciences Faculty, Ferhat Abbas Setif 1 University, Setif, Algeria, between December 2016 and September 2017. Methodology: In vitro antioxidant study was characterized by using free radicals scavenging methods with reducing power, lipid peroxidation and ß-carotene bleaching assays. All tests were realized by spectrophotometric methods. Results: Our study showed that thymoquinone is a potent antioxidant. It is less effective as a scavenger of both DPPH and ABTS radicals with IC50 of 125.65 ± 0.76 and 332.5 ± 14.39 µg/ml, respectively; While it is a strong scavenger of hydroxyl radical with IC50 of 26.3 ± 0.59 µg/ml and very strong hydrogen peroxide scavenger with IC50 of 11.0 ± 0.57 µg/ml. As superoxide anion scavenger it has inhibition ability less than 50%. In lipid peroxidation, TQ had a very efficient activity it inhibits peroxidation of β- carotene by 73.58 ± 0.50%. Thus, in lipid peroxidation assay, TQ had also a significant activity with percent inhibition of 79.5 ± 2.12%. Conclusion: Our results revealed that thymoquinone possesses a low antioxidant activity against DPPH, ABTS and superoxide anion radicals. Thus, it has a very low reducing power capacity, whereas it is a strong hydrogen peroxide, hydroxyl scavenger and lipid peroxidation inhibitor.