Green Synthesis of Copper Nanoparticles Using Aqueous Extract of Grevillea robusta: In Vitro Antimicrobial and In...

Green synthesis of metal nanoparticles using plant-derived phytochemicals offers an environmentally sustainable approach for developing novel antimicrobial agents. In the present study, copper nanoparticles (CuNPs) were biosynthesized using aqueous extracts of fresh and dried leaves of Grevillea robusta with 1 mM copper sulfate under continuous stirring at 80°C. GC-MS profiling identified several bioactive constituents, including palmitic acid and linolenic acid methyl ester, which may contribute to nanoparticle formation and stabilization. Successful synthesis of stable, crystalline, and well-dispersed CuNPs was confirmed by UV-visible spectroscopy, FTIR, SEM, EDX, and XRD analyses. The biosynthesized CuNPs exhibited broad-spectrum antimicrobial activity against clinically and agriculturally important bacterial (Escherichia coli, Xanthomonas axonopodis pv. punicae, Acinetobacter sp., and Citrobacter sp.) and fungal (Colletotrichum sp., Fusarium solani, Fusarium oxysporum, Macrophomina phaseolina, and Alternaria alternata) pathogens, with EC₅₀ values ranging from 2.67-7.23 µg/mL and 2.85-12.65 µg/mL, respectively. Furthermore, CuNPs effectively inhibited biofilm and pellicle formation. Molecular docking demonstrated favorable interactions between selected phytocompounds and microbial target proteins, providing mechanistic support for the observed antimicrobial activity. These findings highlight G. robusta-mediated CuNPs as promising eco-friendly nanomaterials for future antimicrobial applications.