Phytoassisted synthesis of biogenic silver nanoparticles using Vernonia amygdalina leaf extract: characterization, antibacterial, anti-inflammatory, and acute toxicity profile

Increasing antimicrobial resistance and pathological consequences from long-term anti-inflammatory drug use necessitate the urgent discovery and rational design of new, effective antimicrobial and anti-inflammatory agents. This study reports the antibacterial, anti-inflammatory, and acute toxicity profile of Vernonia amygdalina leaf extract-mediated silver nanoparticles (VA-AgNPs). VA-AgNPs were synthesized by mixing Ag+ ions with an aqueous leaf extract from Vernonia amygdalina and characterized using UV-Visible (UV-Vis) spectroscopy, powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). Antibacterial activity against Escherichia coli strains, carrageenan-induced rat paw edema, and oral acute toxicity assays were performed. The change in color from light brown to dark brown indicated the formation of VA-AgNPs, which was further confirmed by the surface plasmon resonance peaks between 400 and 450 nm in the UV-Vis spectrum. Stability studies showed increased VA-AgNPs formation at basic pH and with higher reactant quantities. The X-ray pattern showed nanocrystalline particles of Ag and AgCl with mean sizes of 13 and 18 nm, respectively. The SEM images depict aggregates of spherical shapes. The synthesized VA-AgNPs inhibited Escherichia coli growth with a minimum inhibition concentration of 0.125 mg/mL and rat paw edema with a maximum inhibition percentage of 96% at a dose of 0.4 mg/kg body weight. Oral administration of VA-AgNPs was not associated with any toxicity, supporting their use in the development of new effective antibacterial and anti-inflammatory drugs.