Phytochemical profile of black cumin (Nigella sativa L.) seed oil: identification of bioactive anti-pathogenic compounds for traditional Siddha formulation

Black cumin seed oil has been traditionally used as Karumjeerakam kuzhi thailam (Siddha formulation) in India more than 500 years ago. This study was conducted to find out the bioactive molecules present in black cumin seed oil. The oil was subjected to gas chromatography-mass spectrometry (GC–MS) and liquid chromatography-mass spectrometry (LC–MS) techniques, and the obtained results were compared with the National Institute of Standard Library to identify the presence of chemical compounds. Based on GC–MS and LC–MS analyses, several bioactive compounds were detected such as octanoic acid (m/z 144.21), benzene, 1,3-bis (1,1-dimethyl ethyl) (m/z 190.32), maculosin (m/z 260.1), capric acid (m/z 172.26), 3-ketosphingoshine (m/z 297.3), hygrine (m/z 141.1), tetradecanoic acid, ethyl ester (m/z 256.42), and 2-monomyristin (m/z 302.4). Moreover, the oil was further evaluated for its anti-bacterial activity against both Gram-positive and Gram-negative bacteria and was found that it inhibited the growth of Staphylococcus aureus and Pseudomonas aeruginosa at a concentration of 10 µg/mL. Besides, molecular docking with capric and caprylic acid from the oil has shown a stable binding affinity with major quorum-sensing proteins. Laetisaric acid showed the best binding scores among the 11 compounds selected for the study with the corresponding receptors. These interactions could provide more insight into understanding the action of the identified compounds on various targets.