Identification of Bioactive Compounds Responsible for the Antimicrobial Activity of Nigella Sativa Seed Extracts Using HPLC and Amino Acid Analyser

Nigella sativa medicinal species receiving too much attention in many areas of use, mainly due to its rich source of biologically active constituents in its seeds. Future laboratory research on N. sativa seeds is still required to fully appreciate and support their extensive therapeutic potential in the context of a sound compositional basis. Thus, it was aimed to characterize the main nutrients and active molecules of black cumin seeds and to evaluate, based on phytochemical perspective, the ability of their seeds to inhibit the growth of microorganisms. Proximate analysis revealed good amount of crude lipids (35.70%), carbohydrates (33.34%) and crude proteins (23.2%). The screening performed on free amino acids separated on an amino acid analyzer resolved 16 residues, half of which were the essential amino acids, while the other half were the non-essential ones, and Arginine (44.14 mg/100g) and Glutamic acid (35.65 mg/100g) were the most abundant. The four main phenolic and flavonoids were isolated by HPLC and thymoquinone was the major component (32.5 mg/100 g). Unsaturated fatty acids were the major compounds with linoleic acid (58.57 %) and oleic acid (16.55 %) as the major compounds. The MIC and MBC showed very effective inhibition on all organisms tested, with Alloiococcus otitidis and Staphylococcus aureus being the most susceptible species, followed by Escherichia coli and Klebsiella pneumoniae and finally the fungi, Candida species. All the data together indicate that N. sativa seeds are valuable natural source of therapeutic agents that can fight resistant microbial pathogens.