Green Synthesis of Gold Nanoparticles from Vitex negundo Leaf Extract: Characterization and In Vitro Evaluation of Antioxidant–Antibacterial Activity

Abstract

Vitex negundo a tropical shrub from the Western Ghats possess various medicinal applications. This study reports the antioxidant and antibacterial activities of gold nanoparticles synthesized from V. negundo leaf extracts. The V. negundo leaf extracts were prepared by cold maceration process and green synthesis of gold nanoparticles was performed by gold reduction method. The characterization analyses, such as ultraviolet–visible spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray diffraction, scanning electron microscopy and transmission electron microscopy were carried out. The antioxidant activity of the gold nanoparticles were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and nitric oxide assay. The green synthesized nanoparticles were in the size range of 20–70 nm and exhibited notable antioxidant activity. The IC50 values of DPPH and nitric oxide assays were found to be 62.18 µg and 70.45 µg respectively. In addition, antibacterial analysis of six food borne pathogens (E. coli, B. subtilis, P. aeruginosa, S. aureus, S. typhimurium, and S. pyogenes) was studied by well-diffusion method. The gold nanoparticles displayed strong antibacterial activity against gram negative strains and moderate activity against gram positive strains.