Green Synthesis and Therapeutic Evaluation of Polyphenolic Silver Nanoparticles Derived from Cymbopogon citratus

Abstract Green nanoparticle synthesis has emerged as a sustainable approach in biomedical research, utilizing biological systems such as plants to overcome the limitations of conventional physical and chemical methods. In this study, we biosynthesized silver nanoparticles using plant extract as a capping agent and silver nitrate as a precursor under sunlight. A distinct color change confirmed nanoparticle formation, and UV–visible spectroscopy revealed an absorption peak at 412 nm, while SEM and TEM analyses indicated particle sizes of 1–7 nm. Concurrently, a strain of Salmonella Typhi was obtained from the Central Research and Diagnostic Laboratory, Ilorin, Nigeria, and subcultured on selective and differential media. Identification was confirmed by colony morphology, hydrogen sulfide production, Widal test, and Gram staining. Antimicrobial activity was evaluated using the agar well diffusion method, where standardized inocula were exposed to polyphenolic-rich plant extracts, biosynthesized nanoparticles, and standard antibiotics. Plates were incubated at 37°C for 18–24 hours, and inhibition zones were observed. The results demonstrated enhanced antimicrobial efficacy of the biosynthesized nanoparticles, validating their eco-friendly synthesis and potential biomedical application against Salmonella Typhi.