Biogenic silver and zinc oxide nanoparticles synthesized using Foeniculum vulgare seed extract: Antimicrobial activity and in vivo toxicological evaluation

Abstract

Biogenic synthesis of metal nanoparticles using medicinal plants has emerged as a sustainable and environmentally friendly strategy for producing multifunctional nanomaterials with promising biomedical applications. Here, an aqueous seed extract of Foeniculum vulgare was utilized as a natural reducing and stabilizing agent for the synthesis of silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs). The synthesized nanoparticles were characterized by UV–Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). UV–Visible analysis confirmed nanoparticle formation through characteristic surface plasmon resonance and absorption peaks, while FTIR spectra indicated the involvement of plant-derived phytochemicals in nanoparticle reduction and stabilization. XRD analysis verified the crystalline structure of both nanomaterials, with an average crystallite size of approximately 37 nm, whereas SEM revealed predominantly spherical nanoparticles with diameters ranging from 22 to 128 nm. EDX analysis further confirmed the elemental composition of the synthesized AgNPs and ZnONPs. The antimicrobial performance of the biogenic nanoparticles was investigated against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans using agar well diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal/fungicidal concentration (MBC/MFC) assays. Both AgNPs and ZnONPs exhibited concentration-dependent antimicrobial activity; however, AgNPs produced larger inhibition zones and lower MIC and MBC/MFC values than ZnONPs. Among the tested microorganisms, C. albicans was the most susceptible, whereas P. aeruginosa exhibited the highest level of resistance. The in vivo toxicological profile was evaluated following oral administration of 10 mg/kg/day for 14 consecutive days. AgNP-treated animals showed only minor biochemical and histopathological alterations. In contrast, ZnONP treatment significantly increased serum ALT, AST, and urea levels and significantly decreased ALP activity and the hepato-somatic index compared with the control group (P < 0.05). ZnONP-treated animals also exhibited more pronounced hepatic and renal histopathological alterations than AgNP-treated animals. These findings indicate that F. vulgare-mediated AgNPs provide superior antimicrobial performance with a more favorable short-term safety profile than ZnONPs under the experimental conditions. Collectively, the results highlight the potential of biogenic AgNPs synthesized from F. vulgare seed extract as promising antimicrobial nanomaterials for future biomedical and pharmaceutical applications.