Green Synthesis, Antioxidant and Antimicrobial Activity of Silver Nanoparticles Using Gnetum africanum Extracts

Abstract

The synthesis and application of nanoparticles is an important area of research that is gaining attention recently. In this recent project, we report the synthesis of silver nanoparticles, AgNP using aqueous solution of silver nitrate and Gnetum africanum leaf extract (reducing agent). The synthesis of AgNP was achieved by mixing aqueous solution of silver nitrate (70ml, 15.75mM) with a solution of Gnetum africanum leaf extract 100 ml) in a reaction flask and allowed to stand for 24 hours in a dark cupboard. A color change from light brown to yellowish brown was observed which indicated that synthesis of silver nanoparticles took place. The presence of AgNP was ascertained using UV-vis spectra analysis and absorption at 442 nm showed the presence of AgNP. The antioxidant assay of both the synthesized AgNP and the leaf extract was determined using DPPH. Antimicrobial activity was conducted using three different organisms which were Staphylococcus aureus, Escherichia coli and Pseudomonas respectively. The antioxidant results using DPPH scavenging ability of AgNp showed that at concentrations of 2mg/ml,1mg/ml and 0.1mg/ml, the percentage inhibition  of  DPPH  by AgNp was 61.69, 53.06 and 38.31 respectively and that of Gnetum africanum leaf extract was 81.32, 78.49, and 58.29 respectively at the same concentrations using Ascorbic acid as a standard. The antimicrobial activity of both the synthesized AgNps and Gnetum Africanum Leaf extract using one gram positive bacteria (Staphylococcus aureus) and two gram negative bacteria (Escherichia coli and Pseudomonas) revealed that the synthesized AgNps showed lesser activity than Gnetumafricanum leaf extract for both the gram positive bacteria (Staphylococcus aureus) and gram negative bacteria (Pseudomonas) and (Escherichia coli). From the above findings, it can be observed that Gnetum Africanum Leaf extract reduced Ag+ to Ag0 and also both the synthesized AgNps and the Gnetum Africanum Leaf extract showed reasonable antioxidant activity against DPPH and antimicrobial activity against the tested microorganisms. This implied that both samples have medicinal values.