Abstract

GREEN SYNTHESIS OF SILVER NANOPARTICLES VIA MEDICINAL PLANT EXTRACTS AND THEIR ANTIBACTERIAL ACTIVITIES

Buddhika Indeewarie Keerawelle, Adikari Mudiyanselage Ruhunu Chamara, Gobika Thiripuranathar*

Abstract

The green synthesis of silver nanoparticles (Ag NPs) were studied by bio reduction of silver nitrate solution using extractions of three commonly available medicinal plants found in Sri Lanka. Extractions were prepared using different plant parts obtained from Stachytarphera indica (leaves and stem), Munronia pinnata (leaves and stem) and Rhipsalis baccifera (stem). UV-Visible spectroscopy and Scanning Electron Microscopy (SEM) studies were carried out to confirm, characterize and analyze the physical parameters of produced NPs. The antimicrobial activity of the Ag NPs were evaluated against both gram positive (Staphylococcus aureus, Bacillus subtilis) and gram negative bacteria (Escherichia coli), using broth dilution (MIC) method. The UV-Visible spectroscopy results were discovered to be in the range of 425 nm - 460 nm indicating the formation of Ag NPs by all the plant extracts. SEM analysis confirmed the presence of spherical shaped NPs. The lowest particle diameter was observed for Ag NPs synthesized using Stachytarphera indica leaves extract (39.41 nm) and the highest was reported in Stachytarphera indica stem extract (82.08 nm). The synthesized Ag NPs proven to poses antibacterial activity against all tested pathogens and achieved Total Inhibition Concentration (MIC) value with in the range of 0.250 μg/mL- 0.750 μg/mL of Ag NPs concentration.

Keywords: Silver nanoparticles, antimicrobial activity, green synthesis, plant extracts, antimicrobial activity, broth dilution method.