Green synthesis of silver nanoparticles with Dalbergia spinosa leaves and their applications in biological and catalytic activities

Abstract

The phytosynthesis of silver nanoparticles (AgNPs) by Dalbergia spinosa leaves (DSL) in aqueous extract was investigated. AgNPs were characterized by UV–visible absorption spectroscopy (UV–vis), transmission electron microscopy (TEM) and Fourier transform infra red spectrophotometry (FTIR). The results showed that the increase in the initial extract concentration at room temperature increased the mean size and widened the size distribution of the AgNPs, leading to a red shift and broadening the surface plasmon resonance absorption (439nm). The results showed that the reducing sugars and flavonoids were primarily responsible for the bioreduction of silver ions and that their reductive capability was promoted at 36°C. TEM analysis showed that the AgNPs were nearly spherical in shape with an average size of 18±4nm. When evaluated for in vitro antioxidant activity by DPPH, NO, hydrogen peroxide radicals, reducing power and CUPRAC assay methods in addition to anti-inflammatory activity by HBRC method, the silver nanoparticles exhibited considerably enhanced antioxidant and anti-inflammatory activity at the test doses when compared with that of the standards and the plant extract. Finally, the antibacterial activity of the AgNPs against two Gram-positive bacteria and two Gram-negative bacteria showed moderate antibacterial activity when compared with the standard and the plant extract. The synthesized silver nanoparticles were also effective in the catalytic reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP).