Comparative antibacterial activity of green-synthesized silver nanoparticles and solvent fruit extracts of Acacia nilotica (L.) Willd. against Staphylococcus aureus and Salmonella Typhi

Background: Green-synthesized silver nanoparticles (AgNPs) are utilized to treat antimicrobial-resistant bacteria. This study investigated the antibacterial activity of ethyl acetate, methanolic, and hexane extracts of Acacia nilotica fruits, as well as biosynthesized silver nanoparticles, against Staphylococcus aureus and Salmonella typhi. Methods: Acacia nilotica fruit powders were extracted using methanol, hexane, and ethyl acetate at concentrations of 25%, 50%, and 75% weight per volume. Silver nanoparticles were synthesized from the aqueous extract of fruits and silver nitrate, and the disc diffusion method was performed. Results: Change of solution color, ultraviolet-visible spectroscopy (UV-Vis), and Fourier transform infrared spectroscopy (FTIR) confirmed the successful synthesis of silver nanoparticles (The UV–Vis spectrum showed a surface plasmon resonance (SPR) peak at ∼445 nm). FTIR results indicated the presence of biomolecules involved in silver (Ag+) reduction, including nitro compounds, amides, carboxyl groups, alcohols, benzene, and phenols. Hexane extract with a concentration of 75% inhibited S. typhi (19.67 ± 2.081) and S. aureus (11.33 ± 2.081), whereas Hexane extract with a 25% concentration had no effect against S. aureus. Ethyl acetate extract with 75% concentration inhibited S. aureus (16.33 ± 0.577), while ethyl acetate 75% and 50% and methanol 25% and 75% had no effect on S. typhi. Methanol 75% inhibited S. typhi (13 ± 0.1). AgNPs 25% and 50% inhibited S. aureus (17 ± 1.0 and 15 ± 1.0, respectively) and exhibited low activity against S. typhi. Control showed no inhibition zones. Conclusion: AgNPs of A. nilotica fruit inhibited S. aureus more than S. typhi; for S. typhi, standard antibiotic discs produced measurable inhibition zones. Hexane showed greater efficacy against S. typhi than AgNPs. Further investigations are needed to identify specific antimicrobial components.