Preliminary Screening of Phytoconstituents and Antibacterial Activity of Nigella sativa
Imran Khan* and J. D. Shaikh
Department of Zoology, Maulana Azad College of Arts, Science and Commerce, Aurangabad, India
Nigella sativa (black seed) has been widely used in traditional medicine for its therapeutic properties. This study aimed to evaluate the phytochemical composition and antibacterial activity of Nigella sativa seed extracts against selected bacterial pathogens. Aqueous, ethanol, methanol, acetone, and n-hexane extracts were prepared and subjected to preliminary phytochemical screening, which revealed the presence of alkaloids, flavonoids, phenols, tannins, triterpenoids, proteins, steroids, carbohydrates, glycosides, quinones, and saponins. The antibacterial activity was assessed using the agar well diffusion method against Staphylococcus aureus (MTCC 737), Escherichia coli (MTCC 443), Pseudomonas aeruginosa (MTCC 741), Klebsiella pneumoniae (MTCC 109), Enterobacter aerogenes (MTCC 10208), Salmonella typhi (MTCC 733), and Shigella flexneri (MTCC 1457). The ethanol and methanol extracts exhibited the highest antibacterial activity, with zones of inhibition ranging from 10.5 ± 0.4 mm to 18.5 ± 0.7 mm at 100 mg/mL. Gram-positive bacteria, particularly Staphylococcus aureus, were more susceptible than Gram-negative strains. The aqueous and acetone extracts showed moderate activity, while the n-hexane extract was least effective. The dose-dependent antibacterial activity suggests that higher concentrations of bioactive compounds enhance efficacy. These findings validate the traditional use of Nigella sativa as a natural remedy for infections and highlight its potential as a source of novel antimicrobial agents. The presence of diverse bioactive compounds, such as thymoquinone, flavonoids, and phenols, likely contributes to its antimicrobial properties. Further research is needed to isolate and characterize the active compounds and evaluate their mechanisms of action. This study underscores the importance of exploring plant-based solutions to address the global challenge of antibiotic resistance and supports the integration of Nigella sativa into modern therapeutic applications.
Keywords: Nigella sativa, antibacterial activity, phytochemicals, thymoquinone, antibiotic resistance, traditional medicine
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