Antibacterial and antioxidant studies of silver nanoparticles formulated from Erythrina senegalensis stem bark extract.

Erythrina senegalensis, belongs to the family of Fabaceae and it has been used traditionally to treat microbial infections and diabetes mellitus. The aim of this study was to formulate silver nanoparticles (AgNPs) from the methanol stem bark extract of Erythrina senegalensis and to evaluate the antibacterial and antioxidant effects of the nanoparticles. The methanol extract was screened qualitatively for the presence of tannins, alkaloids, saponins and flavonoids using standard protocols. The silver nanoparticles were synthesized using green method and the particles were evaluated using scanning electron microscope (SEM) and X-Ray diffraction (XRD). The percent inhibition effects of the AgNPs and extract were analyzed using hydrogen peroxide and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. The antibacterial effect of the methanol and the AgNPs were determined by disk diffusion method. The phytochemical screening revealed the presence of tannins and flavonoids. The DPPH assay revealed IC₅₀ values of 3.60, 2.25 and 1.75mg/mL for the silver nanoparticles, methanol extract and ascorbic acid respectively. The findings from this study indicated that the extracts contain some secondary metabolites such as flavonoids which may be responsible for the bio-reduction of silver ion (Ag⁺) to AgNPs as well as the antimicrobial and antioxidant activities.