Green Synthesis of Silver and Zinc Oxide Nanoparticles Using Post-harvest Leaves of Vigna subterranean and their Antimicrobial, Anti-inflammatory and Antioxidant Potentials

Green route synthesis of nanoparticles has been known to be beneficial as one of the non-toxic methods of synthesizing potential drugs. The aqueous extracts of Vigna subterranean (Bambara nut) leaves discarded after harvest were used in the synthesis of silver and zinc nanoparticles using 1mM concentration of silver nitrate (AgNO3) and zinc oxide (Zn O) respectively. The nanoparticles were characterized using Ultraviolet-Visible (UV/Vis) Spectroscopy, Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and X-ray Diffraction Analysis (XRD). Antibacterial and antifungal studies were conducted on two strains of bacteria (Salmonella typhi. and Staphylococcus aureus) and two strains of fungi (Aspergillus niger and Aspergillus flavus) based on their inhibition zone diameter using paper disk diffusion methods. Anti-inflammatory and antioxidant studies were also conducted on the nanoparticles using the inhibition of protein denaturation and reduction of DPPH respectively. The λmax absorption of the nanoparticles were found to be 434 and 460 nm respectively in the UV/Vis region. Their shapes and nature were spherical and amorphous as confirmed by the SEM and XRD analysis. The diameters of the nanoparticles ranged from 20 to 60 nm using the Particle metric particle analysis software. The FTIR confirmed the presence of some bioactive functional groups involved in the reduction of AgNO3 and Zn O to Ag and Zn nanoparticles. The nanoparticles showed moderate activities against the tested bacterial strains while showing no activity against the fungi strain when compared with standard drugs. They however showed strong anti- inflammatory and antioxidant activities. The silver and zinc mediated nanoparticles could serve as a potential source for antioxidants and anti-inflammatory drugs.