GREEN SYNTHESIS OF SILVER NANOPARTICLES FROM THE EXTRACTS OF RUBIA CARDIFOLIA AND MENTHA LONGIFOLIA, AND THEIR ANTIBACTERIAL ACTIVITY STUDIES

Abstract

Using water extracts of medicinal plants in the synthesis of silver nanoparticles, serves both the purposes of reducing agent and stabilizing agent, and hence is greener and economic. The present paper describes the synthesis of silver nanoparticles (AgNPs) from the water extracts of Rubia cardifolia and Mentha longifolia leaves. The particles were characterized using uv-visible extinction spectroscopy, scanning electron microscopy, transmission electron microscopy and powder X-ray diffraction studies. The average sizes of the AgNPs were found to be 28 nm and 24 nm respectively for AgNPs prepared from Rubia cardifolia and Mentha longifolia, and are of face centred cubic structure. Bactericidal effects of the nanoparticles against Escherichia coli (E. coli) and Staphylococcuus aureus (S. aureus) were checked. The AgNPs inhibit the spread of E. coli and S. aureus bacteria to different extents. Bactericidal effect of AgNPs synthesized from the extracts of Rubia cardifolia is found to be good against E. coli with a minimum inhibitory concentration of 70 μg/mL.