Seed oils of Nigella species and of closely related genera

Abstract

Several plant genera belonging to the family Ranunculaceae exhibit highly genus-specific seed ail fatty acid patterns. Seed oils of various Nigella species and of one Garidella species were investigated with regard to their fatty acid composition. All seed oils contained noticeable amounts of dihomo-linoleic acid (20 : 2n-6, or 11,14-cis, cis-eicosadienoic acid, 20 : 2 Delta 11c, 14c). This is in some contrast to published literature on Nigella sativa oils which are used in Mediterranean and Near Eastern countries as an edible oil. investigated were authentic seed oils from Nigella sativa, N. damascena and N. arvensis and also a sample of the very closely related Garidella nigellastrum. Related seed oils (of two Consolida and one Delphinium spp.) and a sample of Turkish a "Corek" spice were also analyzed for comparison. The seed oil fatty acid fingerprints obtained from all the Nigella species show that 20 :2n-6 was the largest peak of the C-20 fatty acids group, i.e. the peak height ratios of 20:2 to 20:2 were reversed from those in most normal vegetable oils. In all Nigella species investigated 20:2 was the much larger peak than 20 : 1. This is believed to be a chemotaxonomic criterium for Nigella, although the fatty acid 20 : 2n-6 has been found also in a number of other Ranunculaceae. In Garidella, 20 : 2n-6 was also present but here 20 : 1n-9 was the larger peak of the C-20 fatty acids group and even approached the levels found in Consolida. The question why in analyses of several commercial types of black cumin oil(Nigella sativa oil) 20 : 2n-6 has not been found could not be solved and needs to be investigated.