Antioxidant and antibacterial activity of silver nanoparticles synthesized by Cestrum nocturnum

BACKGROUND: Silver nanoparticles are toxic to bacteria and have widespread application in different research areas. OBJECTIVE: The aim of this study was to synthesize silver nanoparticles using an aqueous leaf extract of Cestrum nocturnum and to test its antioxidant and antibacterial activities. MATERIALS AND METHODS: The silver nanoparticles were synthesized by addition of 20 ml extract (8% w/v) with 180 ml silver nitrate solution (1 mM). The synthesis of silver nanoparticles was confirmed by UV–Vis spectrophotometer. The silver nanoparticles were characterized by X-ray diffractometer, Transmission Electron Microscope, Scanning Electron Microscope and Fourier Transform Infra-Red spectroscopy. The antioxidant property of silver nanoparticles was analyzed by the 2, 2-diphenyl-1-picrylhydrazyl, hydrogen peroxide, hydroxyl radical and superoxide radical scavenging methods. The bacteriostatic and bactericidal activity of silver nanoparticles against Escherichiacoli, Enterococcusfaecalis, and Salmonellatyphi was determined using bacterial growth inhibition method. The antibacterial sensitivity and Minimum Inhibitory Concentration (MIC) of silver nanoparticles was determined against the bacteria. RESULTS: The results confirmed that the silver nanoparticles synthesized by C.nocturnum extract were crystalline in nature, average particle size was 20 nm and were mostly spherical in shape. The antioxidant methods confirmed that the silver nanoparticles have more antioxidant activity as compared to vitamin C. The silver nanoparticles have strong antibacterial (maximum Vibrio cholerae and minimum E. faecalis) activity. The MIC value of silver nanoparticles was 16 μg/ml (Citrobacter), 4 μg/ml (E. faecalis), 16 μg/ml (S. typhi), 8 μg/ml (E. coli), 8 μg/ml (Proteusvulgaris), and 16 μg/ml (V. cholerae). CONCLUSION: Green synthesized silver nanoparticles have strong antioxidant and antibacterial activity due to the presence of bioactive molecules on the surface of silver nanoparticles.