Phytochemical profiling and eco-friendly synthesis of stable Ag nanoparticles from the extract of Rhizophora mucronata leaves: Comprehensive characterization and antibacterial screening

Silver nanoparticles (AgNPs) were synthesized via a green approach using an aqueous extract of Rhizophora mucronata Lam. leaves as reducing and stabilizing agents. Phytochemical profiling revealed the presence of α-D-mannose, stearamide, and phenolic compounds (pyrogallol, zingerol, and 2-methoxyresorcinol), in which hydroxyl and carbonyl functional groups may contribute to Ag⁺ reduction and nanoparticle stabilization. The formation of AgNPs was confirmed by UV-Vis, FTIR, XRD, SEM-EDS, and TEM analyses. Optimized synthesis conditions (1.25 mM AgNO₃, 0.25% (w/v) extract, pH 8, 60°C, 90 min) yielded predominantly spherical nanoparticles with sizes ranging from 6 to 45 nm (average 27.47 nm) and high colloidal stability (zeta potential −47.4 ± 0.48 mV). Preliminary antibacterial assessment using a disc diffusion assay demonstrated measurable activity against Escherichia coli and Staphylococcus aureus , with inhibition zones of 14.53 ± 0.88 mm and 10.28 ± 0.71 mm, respectively. These findings highlight the potential of R. mucronata -derived AgNPs as eco-friendly nanomaterials with preliminary antibacterial functionality. However, further quantitative evaluation (e.g., MIC/MBC), cytotoxicity assessment, and testing in realistic environmental matrices are required to validate their practical applicability.