Green synthesis of silver nanoparticles using Amaranthus viridis, Mentha piperita and Ocimum basilicum and their in-vitro antioxidant and antifungal activity against Botrytis cinerea

The increasing prevalence of Botrytis cinerea infections has accelerated the need for effective antifungal agents. Traditional chemical methods are often associated with environmental harm, making the green synthesis of nanoparticles an attractive alternative. This study aimed to synthesize and characterize silver nanoparticles (AgNPs) using extracts from three medicinal plants - Amaranthus viridis L., Mentha piperita L., and Ocimum basilicum L. - and evaluate their antifungal efficacy against Botrytis cinerea. AgNPs were synthesized using methanol extracts of the selected plants and characterized by Scanning Electron Microscopy (SEM), UV-visible spectroscopy, X-ray diffraction analysis (XRD), and Fourier-Transform Infrared Spectroscopy (FTIR). The synthesized AgNPs exhibited peak UV-visible absorption at 425 nm, 400 nm, and 420 nm, and had average particle sizes of 1.2 nm, 21.5 nm, and 358 nm for A. viridis, M. piperita, and O. basilicum, respectively. At a concentration of 3%, the AgNPs inhibited B. cinerea growth by 51%, 40.4%, and 39%. Further, an ethyl acetate fraction from A. viridis displayed 50% fungal inhibition at a concentration of 0.20%. GC-MS analysis revealed 15 bioactive compounds in the extracts. The study confirms that AgNPs synthesized from medicinal plants exhibit significant antifungal properties, making them potential candidates for the development of eco-friendly antifungal agents. The findings offer a green and sustainable avenue for the development of new antifungal agents and suggest further studies to optimize the synthesis process and investigate the mechanisms of action.