Green synthesis of silver nanoparticles using Melia azedarach leaf extract and their antifungal activities: In vitro and in vivo

The present work reported the green synthesis, characterization and antifungal activities of silver nanoparticles (AgNPs). The synthesis of AgNPs has been produced by mixing silver nitrate solution with aqueous Melia azedarach leaf extract as a reducing and stabilizing agent for AgNPs. After only 10 min of reaction, the light yellow color of the M. azedarach leaf extract was changed to brown due to the reduction of silver ions to AgNPs, under ambient conditions. The growth of biosynthesized AgNPs was monitored by UV-Visible spectroscopy complemented by dynamic light scattering technique (DLS), zeta potential, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). The peak absorbance of the UV-vis spectra was at 400 nm confirming the formation of silver nanoparticles. SEM analysis shows the existence of small spherical nanoparticles with a size ranged from 18 to 30 nm (average 23 nm). XRD analysis shows that the AgNPs were face-centered cubic (fcc) lattice. The EDS analysis displays intense signals of the silver element. FTIR analysis demonstrated that the hydrolyzable tannic acid involved in M. azedarach leaf extract responsible for the bioreduction and stabilization of AgNPs. The stability of AgNPs was confirmed by zeta potential analysis. A negative zeta potential value of -13.1 mV indicated the stability and good dispersion of AgNPs. The present report aims to point the application of biosynthesized AgNPs as an antifungal agent against Verticillium dahliae in eggplants (Solanum melongena L.) both in vitro and in vivo conditions. For the in vitro condition, it was found that the presence of AgNPs in a concentration of 60 ppm significantly decreased the growth of Verticillium dahlia. However, for in vivo experiment, the presence of 20 ppm of AgNPs reduces the Verticillium wilt severity and relative vascular discoloration, respectively, by 87% and 97%, as compared to inoculated and untreated control. Antifungal activity carried out in this work opens up an important perspective of the biosynthesized AgNPs.