Eco-Friendly Synthesis of Silver Nanoparticles Using Punica granatum (Pomegranate) Peel Extract Under Chemical-Free and Ambient Conditions: Characterization and Antibacterial Activity

In this work, a simple chemical- and thermal-free procedure was developed for the green synthesis of AgNPs using pomegranate (Punica granatum) peel extract as both reducing and stabilizing agents under ambient conditions. The pomegranate extract exhibited a high total phenolic content of 126.37 ± 5.29 mg GAE/g DW, indicating the abundance of bioactive phytochemicals capable of promoting nanoparticle formation. The synthesis parameters were optimized by varying reaction time and extract concentration, with the optimum conditions identified as 18 mg/mL extract concentration and 48 h reaction time based on UV–Vis analyses. The synthesized AgNPs at the optimized condition exhibited a characteristic surface plasmon resonance band at 430–440 nm and were predominantly quasi-spherical with an average particle size of 36.9 ± 14.2 nm determined by TEM. Dynamic light scattering (DLS) analysis yielded an intensity-weighted average hydrodynamic diameter of 72.5 ± 2.4 nm, while the number-weighted distribution confirmed that the suspension was predominantly composed of smaller nanoparticles that were consistent with the TEM observations. The synthesized AgNPs also exhibited a zeta potential of −33.5 ± 0.6 mV, indicating good colloidal stability. XRD and EDX analyses confirmed the formation of crystalline metallic AgNPs, while FTIR results suggested the involvement of phytochemicals in nanoparticle stabilization. The AgNPs also showed concentration-dependent antibacterial activity against E. coli and S. aureus, with MIC (MBC) values of 18.75 (37.5) and 9.375 (150) µg/mL, respectively. In addition, the cytotoxicity assessment using L929 fibroblasts yielded an IC50 value of 86 µg/mL, with a selectivity index of 4.59 and 9.17 against E. coli and S. aureus, respectively, indicating an excellent degree of preferential toxicity toward bacterial cells.