Green synthesis of silver nanoparticles using salvia rosmarinus extract: Characterization, mechanistic antibacterial, antibiofilm, and in silico evaluation

In this study, silver nanoparticles (AgNPs) were synthesized using Salvia rosmarinus (rosemary) extract and evaluated for their antibacterial and antibiofilm efficacy against Pseudomonas aeruginosa. The rosemary-mediated AgNPs (Rm-AgNPs) were characterized using ultraviolet–visible (UV–Vis) spectroscopy (peak at 430 nm), transmission electron microscopy (TEM, ∼31.34 nm), dynamic light scattering (DLS, 281.5 nm), Fourier transform infrared spectroscopy (FTIR), high-resolution X-ray diffraction (HR-XRD), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX), confirming successful biosynthesis, crystallinity, spherical morphology, and stability (zeta potential −21.35 mV). Rm-AgNPs exhibited significant antibacterial activity against P. aeruginosa, with a minimal inhibitory concentration (MIC) of 32.5 µg/mL, and pronounced antibiofilm effects, inhibiting biofilm by up to 65.68 % at 2xMIC. Mechanistic investigations demonstrated that Rm-AgNPs treatment resulted in a substantial increase in reactive oxygen species (ROS) production (3.48-fold increase at 2xMIC), glutathione depletion (21.62 %), and notable leakage of intracellular proteins (4352.38 µg/mL) and DNA (110.35 ng/µL), indicative of severe membrane damage and oxidative stress. Metabolite profiling of rosemary extract via UPLC-HRMS identified multiple bioactive compounds. Molecular docking studies revealed strong interactions between rosemary phytochemicals, notably Alnuside A (docking score −6.81 kcal/mol with LasI) and Umbelliferone (docking score −7.98 kcal/mol with WbpE), and key proteins involved in quorum sensing and biofilm formation. ADMET analysis confirmed good oral absorption, suitable lipophilicity, and low predicted toxicity for Umbelliferone and NP-014904. Toxicity assessments with (Artemia salina) revealed moderate toxicity of Rm-AgNPs, with an LC₅₀ value of 202.55 µg/mL. This study emphasizes the potential of AgNPs derived from S. rosmarinus as sustainable and effective agents against infections associated with biofilms and antimicrobial resistance.