Phytochemical Composition, Antioxidant, Antimicrobial Potential and GC-MS Analysis of Crude and Partitioned Fractions of Nigella sativa Seed Extract

The study aimed to investigate the phytochemical, antioxidant, antimicrobial potential and GC-MS analysis of crude and different fractions of Nigella sativa seed extract. Crude methanol extract of N. sativa seed was obtained, the phytochemical components, antioxidant and antimicrobial potential of the seed were evaluated and the crude extract was partitioned using different solvents. Antimicrobial activity was determined and GC-MS analysis of the fractions was conducted. Saponins, flavonoids, alkanoids (19.8%, 41.6% and 82%), tannins, anthraquinones, terpenoids and steroids were present while cardiac glycosides were not detected. The hexane and chloroform fraction yielded 60.17% and 0.42% from the partitioned crude ex¬tract, respectively. DPPH (2, 2-dipheniyl-1-picrylhydrazyl), total phenolic content and ferric reducing antioxidant power (40.37, 20.1 and 48.4 %) increased in a dose-dependent manner. N. sativa fractions had varied antibacterial activity against the test bacteria and fungi. Staphylococcus aureus ATCC29213 and methicillin-resistant S. epidermidis3 were highly susceptible (60.0 mm and 56.0 mm) to chloroform fractions while Trichophyton sp. and Candida tropicalis had the highest susceptibility (50 mm) to the hexane fraction. A total of 24 dis¬tinct phyto-components were identified, and 9, 8, 7, 3 and 4 compounds were found in the hexane, meth¬anol, ethyl acetate, chloroform fractions and the crude extract. The compounds were 2-Chloroethyl vinyl sulfide, 11-Octadecenoic acid, methyl ester, Cyclononene, 3,8-Dioxatricyclo[5.1.0.0(2,4)] octane, 4-ethe¬nyl-, 7-Hydroxy-3-(1,1-dimethylprop-2-enyl)coumarin, Trimethylsilyl-di(timethylsiloxy)-silane among others. The crude, hexane and chloroform (%) fractions contained 99.3%, 96.42% and 97.90%, respectively, of Trimethylsi-lyl-di(timethylsiloxy)-silane. In conclusion, the N. sativa seed extract contains good phytochemicals, anti¬oxidant and varied antimicrobial activities against the test pathogens.