Synthesis of AgNPs Using Binary Mixture Extract of Moringa Oleifera and Bauhinia Variegata for Antioxidant Studies

Abstract

Green synthesis of silver nanoparticles (AgNPs) using plant extracts offers a cost-effective, scalable, and eco-friendly alternative to conventional chemical or physical methods. In this work, AgNPs were synthesized and optimized using a binary aqueous leaf extract of Moringa oleifera and Bauhinia variegata, and their antioxidant activity was evaluated. Different extract ratios were prepared and their reducing capacities assessed. Optimal synthesis conditions (extract:AgNO₃ ratio, pH, temperature, reaction time) were established by monitoring solution color change and UV–Vis surface plasmon resonance (SPR) peaks. The synthesized AgNPs were characterized by UV–Vis spectroscopy, FTIR, XRD, SEM/TEM, and DLS (zeta potential) to assess their optical properties, surface functional groups, crystallinity, morphology, and colloidal stability.

Antioxidant assays (DPPH, ABTS, and FRAP) were conducted with ascorbic acid and BHT as reference standards. The AgNPs exhibited a distinct SPR band at ~400–450 nm, and SEM/TEM images showed spherical particles with a narrow size distribution; XRD confirmed a face-centered cubic (fcc) crystalline lattice. FTIR analysis indicated phytochemical compounds capping the nanoparticle surfaces. Notably, the AgNPs demonstrated enhanced antioxidant activity, with higher FRAP values and lower IC₅₀ values in DPPH and ABTS assays compared to the crude extracts, suggesting synergistic effects. Finally, potential biomedical and nutraceutical applications, plausible reduction/stabilization mechanisms, scale-up strategies, in vivo biocompatibility testing, and study limitations are discussed.