Synthesis and characterization of Silver nanoparticles from fruit extract of Michelia Champaca L.: Their antioxidant and antibacterial activity

Plant mediated synthesis of silver nanoparticles (AgNPs) is considered as a representative approach in material synthesis for environmental benignity. In this paper, we report an eco-friendly (green) protocol for the preparation of AgNPs using fruit extract of Michelia champaca L. The color change in experimental solution from light brown to dark brown indicates the resonance of AgNPs and further confirmed by characteristic Surface Plasmon Resonance (SPR) absorption peak at 410 nm using UV-Vis spectroscopy. Fourier Transform Infrared Spectroscopy (FTIR) analysis confirms the presence of phytochemicals like phenols and flavonoids in the fruit extract which are responsible for reduction and stabilization of AgNPs. The biocapping molecules of nanoparticles were possibly stable and were negatively charged as revealed by zeta potential measurement. Further, the size and morphology of the nanoparticles were studied by using Atomic Force Microscopy (AFM) and High Resolution Transmission Electron Microscope (HRTEM) analysis. The AgNPs were evaluated for antioxidant and antibacterial activities. The DPPH radical scavenging assay showed good antioxidant activity of AgNPs (EC50= 532.16 µg/mL) when compared to both fruit extract (EC50= 261.08 µg/mL) and standard ascorbic acid (AS) (EC50= 426.04µg/mL). The AgNPs exhibited potent antibacterial activities against both gram positive and gram negative bacteria. The Pseudomonas aeruginosa (19.00±0.73a mm) showed the highest zone of inhibition at 1000µg/ml concentration of AgNPs solution followed by Staphylococcus aureus (9.00±0.14a mm), Bacillus cereus (10.00±0.19a mm) and Escherichia coli (10.66±0.18a mm). Finally, it can be concluded that AgNPs from Michelia champaca fruit extract showed distinctive free radical scavenging and potent antibacterial activity.