Silver nanoparticles biosynthesized by secondary metabolites from Moringa oleifera stem and their antimicrobial properties

Biological extracts have recently shown a great potential for rapid biosynthesis of silver nanoparticles (AgNPs) with antibacterial activity. AgNPs were synthetized by reduction effect of secondary metabolites produced by the Nigrospora sp. fungus, from Moringa oleifera stem as a reducing agent and silver nitrate (AgNO3) (1 mM) as salt precursor. The synthesis of nanoparticles (NPs) was monitored through analysis of the UV-Vis spectroscopy absorption in the 436 to 440 nm range indicating the presence of AgNPs in the colloidal aqueous solutions. Fourier transform infrared spectroscopy (FTIR) spectra were performed to identify the compounds responsible for the bio reduction of the Ag+. The morphology and sizes of AgNPs were characterized by scanning electron microscopy (SEM), energy dispersive of X-ray spectroscopy (EDS), dynamic light scattering (DLS), and colloid stability by zeta potential measurements. The NPs obtained were spherical in shape with size in the 3 to 70 nm range. Antibacterial activity was confirmed by evaluation of their effect against Escherichia coli, Klebsiella cloacae and Staphylococcus epidermidis. The proposed green synthesis of AgNPs from secondary metabolites produced by the Nigrospora sp. fungus from M. oleifera stem can be strongly recommended as a potential method for biomedical application. Key words: Silver nanoparticles, secondary metabolites, green chemistry, antibacterial activity.