Exploring the Antibacterial, Antioxidant and Larvicidal Effects against Culex quinquefasciatus of Nigella sativa Seeds and its Silver Nanoparticles.

Objective: Lymphatic filariasis is a debilitating disease where progression from acute to chronic stages is often exacerbated by secondary bacterial infections, facilitated by normal skin microbiota. The disease is transmitted by Culex quinquefasciatus, which also carries other diseases.

Methods: Nigella sativa seeds possess antibacterial properties effective against Gram-positive and Gram-negative bacteria, and exhibit larvicidal activity against various mosquito larvae. In this study, aqueous extracts of N. sativa seeds and synthesized silver nanoparticles (AgNPs) were evaluated for antibacterial efficacy against Bacillus subtilis, Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, and Salmonella typhi. Antioxidant activity was assessed using the DPPH assay. Larvicidal activity against Culex (Cx.) quinquefasciatus was also evaluated.

Results: The aqueous seed extract (100 mg/mL) and extract-synthesized silver nanoparticles (AgNPs) (100 µg/mL) exhibited significant antibacterial activity. Notably, both also showed considerable antioxidant activity at a concentration of 100 µg/mL. Larvicidal activity revealed LC₅₀ values of 33.88 ppm for the seed extract and 0.52 ppm for extract-synthesized AgNPs.

Conclusion: The findings suggest that N. sativa seeds and their extract-synthesized AgNPs have strong potential for mosquito control and managing secondary bacterial infections in lymphedema, particularly if formulated as an ointment. Further research on ointment formulations could enhance their public health applications.