Antioxidant and antifungal efficacy of green synthesized silver nanoparticles

Abstract

The use of herbs have gained momentum in the contemporary research, as they possess several biological activities. Green synthesised nanoparticles are extensively under exploration due to their multi-faceted roles. The present work details the comparative antioxidant potentials of the leaves and seeds extracts of the herbs Coriander sativum (coriander), Trachyspermum ammi (Ajwain), Trigonella foenum-graecum (menthi) and synthesis of silver nanoparticles. The antifungal effects of the synthesized nanoparticles against a pathogenic species of Aspergillus flavus and the mode of action was also analysed. Results of the investigation showed that the seed extract of Ajwain and leaf extract of coriander exhibited the highest antioxidant properties and were used as reducing agents for silver nanoparticles synthesis. The nanoparticles were characterized by UV-visible absorption spectrum, Scanning Electron Microscopy-Energy Dispersive Spectra (SEM-EDS) and Transmission Electron Microscopy (TEM). The silver nanoparticles showed enhanced antioxidant activity when compared to the extracts. The antifungal studies showed that both the nanoparticles were effective against A. flavus, while C. sativum silver nanoparticle (Cs-AgNP) exhibited the highest activity. The mechanism of antifungal effect showed that the nanoparticles exerted a membranolytic activity on the pathogenic A. flavus. SEM images showed highly wrinkled mycelia in nanoparticles-treated samples and membrane permeabilization was evident from the 1- N-phenyl napththyl amine assay in nanoparticle-treated fungal samples. The activity of a transmembrane enzyme calcium ATPase was also significantly decreased in treated samples confirming the membrane damage effects of nanoparticles. Among the nanoparticles, Cs-AgNP showed the maximum effect. The efficacy of these green synthesized nanoparticles provides insight into their use as effective antifungal agents.