Green synthesis of gold nanoparticles using Telfairia occidentalis leaf extract and evaluation of their antioxidant activity for possible industrial applications

Abstract

An investigation was conducted on the green synthesis of gold nanoparticles (AuNPs) using aqueous Telfairia occidentalis leaf extract as both the reducing and stabilizing agent. Following preliminary phytochemical analysis, AuNPs were synthesized by reacting aqueous tetrachloroauric acid trihydrate with the extract under controlled conditions and characterized using several analytical techniques. The UV-visible spectrum exhibited a surface plasmon resonance (SPR) band at 547.92 nm, and Fourier-transform infrared (FTIR) spectroscopy revealed hydroxyl and amide functional groups, supporting stabilization by polyphenols and proteins. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) supported a quasi-spherical morphology and high crystallinity, with a mean diameter of 25.89 ± 7.53 nm, a size range of 10.81--48.31 nm, and a median diameter of 25.26 nm (n = 108), as determined using ImageJ; energy-dispersive X-ray spectroscopy (EDS) confirmed the elemental composition and predominance of gold. Antioxidant capacity evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and lipid peroxidation inhibition assays was concentration dependent. At 100 mu g/mL, AuNPs gave 68.20 ± 0.20% DPPH inhibition versus 91.66 ± 0.26% for ascorbic acid, 75.81 ± 0.18% FRAP versus 95.88 ± 0.38%, and 65.90 ± 0.40% lipid-peroxidation inhibition versus 89.25 ± 0.40%. The findings indicate promising in vitro antioxidant activity, although safety, stability, and application-specific performance require further validation before biomedical or industrial use.