Screening of Antibacterial and Antioxidant Activity of Biogenically Synthesized Silver Nanoparticles from Alternaria alternata, Endophytic Fungus of Dendrophthoe falcata-a Parasitic Plant

The present research was aimed to synthesize and characterize silver nanoparticles (AaAgNPs) using endophytic fungus, Alternaria alternata from the plant, Dendrophthoe falcata. The endophytic fungal water extract was used to prepare silver nanoparticles and the colour of the reaction mixture was changed to light brown colour after 24 h of incubation. The endophytic fungal phytochemicals might have aided in the bioreduction of silver nitrate to silver nanoparticles thus changing the colour of the reaction mixture. Both endophytic fungal extract and endophytic fungal extract mediated NPs shown different phytochemicals in GC–MS analysis. The synthesized silver nanoparticles were characterized using UV–visible spectroscopy, XRD, FTIR, EDX, DLS, SEM and TEM to study structure, size, and shape of the nanoparticles. The AaAgNPs found to be spherical with an average particle size of 66 to 88.6 nm. Significantly, the AaAgNPs have inhibited the growth of Bacillus cereus followed by Klebsiella pneumoniae, Pseudomonas aeruginosa, E.coli, Staphylococcus aureus, and Proteus mirabilis exhibiting antibacterial activity. Overall, the AaAgNPs had shown significant antibacterial property. The AaAgNPs had shown potent antioxidant activity in four different methods (DPPH radical scavenging assay, Hydrogen peroxide scavenging assay, Nitric oxide radical scavenging activity, Reducing power assay) and the activity was more compared to standard used. This is the pioneering report on the study of antibacterial and antioxidant activity of AaAgNPs, synthesized from endophytic fungus, Alternaria alternata of D. falcata.