Biosynthesis and Characterization of Silver Nanoparticles from Methanol Leaf Extract of Cassia didymobotyra and Assessment of Their Antioxidant and Antibacterial Activities.

The biosynthesis of silver nanoparticles (AgNPs) was achieved for the first time using methanol leaf extract of C. didymobotyra and their in vitro antioxidant and antibacterial activities were also evaluated. Methanol leaf extracts of C. didymobotyra after mixing with AgNO3 solution showed the change in color from light brown to dark yellowish brown within 1 hour. UV-visible spectroscopy study showed the surface plasmon resonance at around 420 nm clearly indicating the biosynthesis of AgNPs. Transmission Electron Microscopy (TEM) analysis proved the presence of biosynthesized AgNPs in spherical shape with huge disparity in sizes. The average size of biosynthesized nanoparticle was about 18 nm. The occurrence of face centered cubic shapes of nanoparticles was established by X-ray diffraction (XRD) patterns. Further, Fourier transform infrared spectroscopy (FTIR) study showed the possible capping of AgNPs because of the active biomolecules present in the methanol leaf extract of C. didymobotyra. The antioxidant activities of biosynthesized AgNPs were evaluated by 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging assay and found that AgNPs demonstrated a strong antioxidant properties compared to methanol leaf extract. Nevertheless, the biosynthesized AgNPs exhibited a strong antibacterial activity against all the tested human pathogenic bacterial strains compared to crude methanol leaf extract of C. didymobotyra. Thus, it is concluded that these biosynthesized AgNPs are cost effective, eco-friendly in nature and could be applied for developing new antibacterial drugs and other biomedical applications in near future.