Effects of volatile oil and nonsaponifiable fractions from nigella sativa oil and it’s constituent, thymoquinone against cardiovascular risk parameters in experimental hyperlipidemia

Abstract

The combined in vitro and in vivo results presented in the thesis can be summarized as follows: Nigella sativa (NS) seed oil and it s methanol (NSF) or volatile oil (VO) extracts contained significant amounts of natural antioxidants, which directly react with and quench stable DPPH, cation ABTS and NO radicals and also possessed an effective OH radical scavenging activity in both the assay for the deoxyribose test and nonenzymatic lipid peroxidation in phospholipid liposomes. The presence of good quantity of phenolic compounds in NS seed oil, NSF and VO extracts may contribute to overall antioxidant activities. In addition, a significant chelating activity against Fe+2 in the oil and it s extracts suggest an in vivo preventive role in the free radical mediated oxidative damage. The data revealed that all the antioxidants, present in the thymoquinone (TQ) rich VO extract of NS seed oil, responsible for DPPH scavenging activity, were fully fractionated in NSF extract of oil. The comparison of scavenging activities of NS seed oil and it s NSF and VO extracts with pure TQ and pure limonene (LMN), two constituents of VO, against DPPH , OH, ABTS + and NO revealed a two-fold lower IC50 value for NSF, compared to VO, in the order NSF gt pure TQ gt NS oil gt pure LMN. Consistent with these results, TQ rich NSF extract exhibited a 2-fold higher inhibition of nonenzymatic lipid peroxidation in phospholipid liposomes by reducing the formation of MDA, which is mediated by a significantly stronger OH radical-scavenging activity compared to TQ rich VO extract of NS seed oil. Taken together, these findings demonstrate that 100 % higher quenching efficiencies of NSF extract against the above four free radicals are apparently due to the presence of all the radical-scavenging agents associated with VO extract plus good amount of mixture of phytosterols, known to exhibit strong antioxidant activity, are also extracted out in methanol as NSF from fixed oil portion of NS seed oil.