PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

Green synthesis of metallic nanoparticles offers a sustainable alternative to conventional chemical methods, providing enhanced biocompatibility and reduced environmental impact. In this study, gold nanoparticles (AuNPs) were synthesized using Elaeocarpus ganitrus (Rudraksha) leaf extract, which functioned as a natural reducing and stabilizing agent. Reaction optimization revealed that 1000 µM HAuCl₄, a 1:9 extract-to-precursor ratio, and alkaline pH 10 produced the most uniform and stable nanoparticles, confirmed by a sharp surface plasmon resonance peak at approximately 530 nm. FTIR analysis indicated that hydroxyl, carbonyl, and amide-containing phytoconstituents facilitated both metal ion reduction and nanoparticle capping, while XPS confirmed complete conversion of Au³⁺ to metallic Au⁰. SEM micrographs showed faceted nanoparticles ranging from 20–80 nm, and DLS measurements revealed a hydrodynamic size of ~120 nm, consistent with an organic capping layer. The biosynthesized AuNPs exhibited potent antimicrobial effects, demonstrating over 60% inhibition of Escherichia coli and substantial suppression of Aspergillus niger growth in a dose-dependent manner. Cytotoxicity evaluation in 3T3-L1 fibroblasts showed high biocompatibility at lower concentrations, with cell viability exceeding 80% up to 50 µg/mL and an estimated IC₅₀ of 180–220 µg/mL. The findings highlighted Rudraksha- mediated AuNPs as promising candidates with strong antimicrobial potential and excellent biocompatibility.