Phyto-mediated silver nanoparticles via Mellisa officinalis aqueous and methanolic extracts: synthesis, characterization and biological properties

Abstract The aim of the study was to examine the influence of extraction method on the size, shape and morphology of synthesized silver nanoparticles (AgNPs). Silver nanoparticles were prepared by the aqueous and methanolic extracts of lemon balm. The properties of obtained nanoparticles were characterized by UV-Vis, SEM, XRD and FTIR techniques. The UV-Vis spectroscopy confirmed the formation of AgNPs by observing a distinct surface Plasmon resonance band around 450 nm. SEM images showed different shape, size and morphology of AgNPs using two different extracts types. AgNPs derived from the aqueous extract were rod-shaped with a diameter of 19 to 40 nm whereas spherical particles were synthesized by the methanolic extract found smaller with size distribution ranging from 13 to 35 nm. The XRD pattern indicated that AgNPs formed by the reduction of Ag + ions using methanolic extract of M. officinalis were crystal-like in nature. The functional groups of M. officinalis methanolic extract involved in synthesis and stabilization of AgNPs were investigated by FTIR. In addition, AgNPs-containing methanolic extract showed higher antioxidant activity. These particles exhibited remarkable antimicrobial activity against gram positive and negative bacteria and a fungus. The nanoparticles produced by the methanolic extract of the lemon balm showed antioxidant and antimicrobial activity. The production of silver nanoparticles using plant extract is rapid, low cost and eco-friendly. Therefore, green chemistry is a good alternative to industrial production of nanoparticles. Silver nanoparticles can be used as an antiseptic to sterilize the surrounding area and the hospital wastes.