Sunlight-Driven Instant Synthesis of Silver Nanoparticles Using Aqueous Fruit Extract of Terminalia Paniculata Roth and in Vitro Assessment of Its Antioxidant and Anti-Inflammatory Activities

Abstract

Herein we report a sunlight-driven, instant, one-step, green route for the synthesis of silver nanoparticles (AgNPs) using aqueous fruit extract of Terminalia paniculata Roth and in vitro assessment of its antioxidant and anti-inflammatory activities. 5 mL of aqueous fruit extract of T. paniculata was added to 95 mL of 1 mM AgNO3 and exposed to direct sunlight. The T. paniculata fruit extract mediated AgNPs (TpF-AgNPs) were characterized for their morphological, physical, and chemical properties using UV-Vis Spectroscopy, Fourier-Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM) and High-Resolution Transmission Electron Microscopy (HR-TEM) with Selected Area Electron Diffraction (SAED). The antioxidant activity of TpF-AgNPs was evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging assay and the anti-inflammatory activity by Bovine Serum Albumin (BSA) anti-denaturation assay at different doses. The formation of TpF-AgNPs was observed as a colour change from pale-yellow to reddish-brown within 3 mins under direct sunlight. UV-Vis spectra revealed an absorption peak at 411 nm, which is the characteristic for silver nanoparticles. FTIR spectra revealed the possible functional groups of phytochemicals such as -OH and -NH involved in the reduction and capping of TpF-AgNPs. HR-TEM analysis confirmed the spherical shape of nanoparticles with sizes ranging from 5-50 nm with an average particle size of 26 nm. AFM shows surface topography of TpF-AgNPs. The crystalline nature with Face Centered Cubic structure was confirmed through XRD and SAED. The negative value of zeta potential (-53.9 mV) indicated the excellent stability of nanoparticles. The TpF-AgNPs exhibited maximum % scavenging of 71.72 ± 0.51 at 100 µg/mL for antioxidant activity and maximum % inhibition of 85.88 ± 1.09 at 500 µg/mL for anti-inflammatory activity. The sunlight-driven green synthesis of TpF-AgNPs proved to be an instant method in the formation of small-sized nanoparticles exhibiting good antioxidant and anti-inflammatory activity.