Environmentally benevolent synthesis and characterization of silver nanoparticles using Olea ferruginea Royle for antibacterial and antioxidant activities

In this study, we reported an easy, rapid, cost-effective and environmentally benign method for the fabrication of silver nanoparticles (Ag-NPs) using Olea ferruginea as reducing, capping and stabilizing agent. For this, an aqueous extract of leaf and bark of O. ferruginea was treated with 1 mM AgNO 3 , which reduces Ag ions to Ag-NPs by establishing reddish brown color. The synthesized Ag-NPs were spherical crystals, with a mean size of 23 and 17 nm for leaf- and bark-mediated Ag-NPs, respectively. Fourier transform infrared spectroscopy affirmed the role of leaf and bark extracts of O. ferruginea as reducing, capping and stabilizing agent. These biosynthesized Ag-NPs showed profound antibacterial activity against Gram-negative ( Pseudomonas aeruginosa and Escherichia coli ) and Gram-positive ( Streptococcus pneumonia and Staphylococcus aureus ) bacteria. The highest antibacterial activity was shown by bark Ag-NPs against S. aureus (14.00 mm), while leaf Ag-NPs showed higher activity against S. pneumonia (13.00 mm). Additionally, they produced effective antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) as compared to plant extracts and positive control. It was observed that the bark-mediated Ag-NPs had higher percentage (90%) of scavenging potential than the leaf-mediated Ag-NPs (78%). The significance of the current study is the synthesis of eco-friendly, easy and cost-effective Ag-NPs as biomedical products.