Volatiles distribution in Nigella species (black cumin seeds) and in response to roasting as analyzed via solid-phase microextraction (SPME) coupled to chemometrics

Nigella sativa is a crop grown worldwide for its seeds oil production, nutritive value and health benefits. Despite extensive studies on Nigella seed non-volatile metabolites, much less is known regarding volatiles composition within that genus. To gain insight into Nigella species aroma, 34 volatile constituents from 12 Nigella accessions were profiled using headspace solid-phase microextraction (SPME) coupled to mass spectrometry. Aromatics amounted for the major volatile class among N. sativa accessions at ca. 99.8% with thymoquinone as a major component. Variation in thymoquinone levels were evident among N. sativa accessions and also recognized as potential marker for identifying N. sativa from its closely allied drugs. In contrast, sesquiterpenes dominated N. arvensis, N. damascena, N. nigellastrum and N. orientalis volatile blends. Compared to N. sativa fresh seeds, roasted seeds and fixed oil preparation were both found less enriched in thymoquinone and more dominated by its immediate precursor p-cymene.