Chemical composition and in vitro bioactivity of the volatile and fixed oils of Nigella sativa L. extracted by supercritical carbon dioxide

Nigella sativa L. (Ranunculaceae), commonly known as ‘black cumin’, is an erect herbaceous annual plant. N. sativa seeds have traditionally been used in folk medicine as a natural remedy for various diseases as well as a spice. The seeds contain both fixed and essential oils, proteins, alkaloids and saponins. Much of the biological activity of the seeds has been shown to be due to thymoquinone, the major component of the essential oil. The fixed oil is composed mainly of unsaturated fatty acids, including the unusual C20:2 eicosadienoic acid.Isolation of volatile and fixed oils from N. sativa seed of Turkey and Egypt has been obtained by supercritical fractioned extraction with carbon dioxide. Extraction experiments were carried out at pressures of 90 and 300 bar and temperature of 40 °C. The extraction step performed at 90 bar produced a volatile fraction mainly formed by tymoquinone (79 ÷ 86%) and o-cymene (5 ÷ 11%). The oil yield relative to this step of the process was 0.1 ÷ 0.3% by weight of the charge. The last extraction step at 300 bar produced a fixed oil. The yield of this step was 21–26% by weight. The most represented fatty acids of fixed oil from N. sativa were 18:2 n − 6 (54 ÷ 55%), 18:1 n − 9 (22 ÷ 23%), 16:0 (12 ÷ 13%), 18:0 (3%), and 20:2 (2 ÷ 3%).The volatile and fixed oils obtained from N. sativa were evaluated for the antibacterial activity by employing standard strains of Escherichia coli, Pseudomonas aeroginosa, Acinetobacer baumannii, Staphylococcus aureus, Enterococcus faecalis. In vitro antifungal activity of the derivatives against Candida albicans, C. tropicalis, and C. krusei were screened by using ketoconazole, and fluconazole as control agents. The anti-mycobacterium activity breakpoint concentration (μg mL−1) was determined against standard strains of Mycobacterium tuberculosis H37Rv and M. avium (ATCC 15769). The volatile and fixed oils displayed antimicrobial activity toward all of the standard (ATCC, RSKK) strains of the tested bacteria at MIC values of 8–64 μg mL−1 and were revealed to be ineffective against isolated strains (MIC; >256 μg mL−1). The volatile and fixed oils emerged as effective against the bacteria of M. avium with MIC values of 8 μg mL−1. Moreover, all the extracts exhibited antifungal activity against C. albicans, C. tropicalis, and C. krusei at MIC values of 16–64 μg mL−1.

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► Volatile/fixed oils were extracted by SFE-CO2 from Nigella sativa seeds of Turkey/Egypt.
► Essential oils were mainly composed by the oxygenated monoterpene thymoquinone.
► Fixed oils showed high level of unsaturated fatty acids, mainly essential 18:2 n − 6.
► Volatile/fixed oils displayed interesting antituberculosis and antifungal activities.
► Results confirm N. sativa oils as a potential resource for food/pharmaceutical applications.