Phytochemical‐Mediated Synthesis of Silver and Gold Nanoparticles From Piper ornatum : Characterization, Antibacterial Efficacy, and Anticancer Mechanisms

This study presented the green synthesis and biological properties of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) using Piper ornatum leaf extract. UV–Vis spectroscopy revealed characteristic surface plasmon resonance peaks at 420–440 nm for AgNPs and ∼550 nm for AuNPs, confirming successful nanoparticle formation. Size analysis showed AgNPs were considerably smaller (4–33 nm; average 14.74 nm) than AuNPs (67–496 nm; average 263.17 nm). FTIR analysis indicated that plant compounds containing hydroxyl, carbonyl, amine, and polysaccharide groups were responsible for reducing metal ions and stabilizing the nanoparticles. When tested for antimicrobial activity, AgNPs showed dose‐dependent inhibition of both Staphylococcus aureus and Escherichia coli , with both the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 6.25 mg/mL. On the other hand, AuNPs displayed no antibacterial effects. In cancer cell studies, AgNPs significantly reduced MCF‐7 breast cancer cell viability in both a dose‐ and time‐dependent manner, with half‐maximal inhibitory concentration (IC 50 ) values decreasing from ∼35 at 24 to ∼18 µg/mL at 72 h. AuNPs had minimal impact on cell viability, maintaining > 80% viable cells across all tested concentrations. The selective cytotoxicity of AgNPs was further supported by their lack of toxicity toward the noncancerous breast cell line MCF‐10A. Further investigation revealed that AgNPs suppressed several cancer‐related genes ( c-Myc , Cyclin D1 , HER2 , COX-2 , and miR-622 ) and triggered changes in nuclear structure typical of cell death through apoptosis. These results demonstrated that P. ornatum extract effectively produces nanoparticles through green synthesis, with AgNPs showing particular promise for both antibacterial and anticancer applications, while AuNPs appear better suited for biocompatible applications.