Green Synthesis of Silver Nanoparticles Using Hagenia abyssinica (Bruce) J.F. Gmel Plant Leaf Extract and Its Antibacterial and Anti-Oxidant Activities

Abstract

A fast, efficient, simple and environmentally-friendly, green synthesis method was employed for the synthesis of silver nanoparticles (AgNPs) using easily available, low-cost and non-toxic Hagenia Abyssinica plant leaf extract from Ethiopia. The AgNPs formation was confirmed by UV–Vis spectroscopy. Spectrophotometrically, the synthesized silver nanoparticles in solution have shown maximum absorbance at 430 nm. The different parameters like temperature, pH, time, silver nitrate concentration and volume of leaf extract were optimized spectrophotometrically. Fourier-Transform Infrared (FTIR) Spectroscopy was utilized and the FTIR spectroscopy confirmed the existence of various functional groups responsible for reducing and stabilizing during the biosynthesis process. Furthermore, the X-ray Diffraction (XRD) technique was used to confirm the structure, crystal size and nature of the AgNPs. Based on the XRD result, the synthesized AgNPs consists of Ag metal, crystalline in nature with face centered cubic geometry and the average crystallite sizes of the particles were 22.2 nm. The anti-bacterial activity of the synthesized AgNPs and plant leaf extract against gram-negative bacteria (klebsiella pneumoniae and salmonella typhimurium) and gram-positive bacteria (Streptococcus pneumoniae) were determined by standard agar well diffusion method. The anti-oxidant property of synthesized AgNPs was analyzed by the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical scavenging assay method. The synthesized AgNPs have strong anti-bacterial activity against gram-negative (S. typhi) bacteria with inhibition zone of 18.3 mm with respect to the highest concentration (200 μg/ml) as compared to the plant leaf extract against the same bacteria strain with Zone of Inhibition (ZOI) recorded as 13 mm with the highest concentration of 200 μg/ml. The anti-oxidant methods confirmed that the silver nanoparticles have high anti-oxidant activity (66% with the largest tested concentration of 320 µg/ml). The developed method for the silver nanoparticles synthesis using Hagenia Abyssinica plant leaf extract is an eco-friendly and convenient method. In near future, the synthesized AgNPs could be used in the fields of water treatment, biomedicine, biosensor and nanotechnology.

Keywords: Anti-bacterial activity, anti-oxidant activity, green synthesis, Hagenia Abyssinica, silver nanoparticles