Sustainable Green Synthesis of Copper Nanoparticles from <i>Oroxylum indicum</i> Leaves and Evaluation of Their Medicinal Applications

Abstract Copper nanoparticles (CuNPs) from the leaves of Oroxylum indicum (L.) Benth. ex‐Kurz (OIL) were synthesized by using the green chemistry approach. The green synthesized CuNPs were characterized by using the UV–vis., FTIR, SEM‐EDX, and XRD techniques. It was observed that 1:3 (metal to plant extract) was the best ratio at pH 5.50, and temperate at 80 °C for better yield. Advanced characterization has revealed that the shape of CuNPs was spherical with size 30 ± 5 nm. Comparative medicinal applications of CuNPs and OIL were tested where antioxidant and antibacterial potential analysed. In DPPH assay the IC 50 value for CuNPs and OIL was 2.23 ± 0.148 and 79.01 ± 4.151 mg/mL, respectively. In DPPH assay, superior antioxidant action of CuNPs over OIL extract was observed. In comparative antibacterial studies of CuNPs and OIL extract, almost double activities were noticed for CuNPs with an order Salmonella typhi &gt; Staphylococcus aureus &gt; Escherichia coli &gt; Pseudomonas aeruginosa . The results of present study suggest the green synthesis of CuNPs by using leaf extract which is an underutilized part. The applications of CuNPs in medicines, fuel cell, food storage industries may be done after the in‐depth toxicity studies of CuNPs.