Green Synthesis of Silver Nanoparticles from Cotoneaster lacteus: Experimental Characterization and Mechanistic Insights from Biological Assays, DFT and Molecular Docking Studies.

In this study, silver nanoparticles were green synthesized using Cotoneaster lacteus and characterized for the first time in a comprehensive way. The phytochemical composition of the extract was analyzed by GC-MS/MS and LC-ESI-MS/MS, and the main constituents were identified as linoleic acid (63.56%) and trans-ferulic acid (55.94 ng/mL). The C. lacteus extract-based AgNPs were characterized using UV-Vis, FT-IR, XRD, SEM-EDX, STEM, and zeta potential analyses. XRD results showed a face-centered cubic crystal structure with an average crystallite size of 25.42 nm, while STEM images indicated predominantly spherical particles with an average size of 20.75 ± 3.79 nm. In the biological assays, C. lacteus extract-based AgNPs showed noticeably higher antibacterial activity compared to both the crude extract and AgNO₃. Antibiofilm inhibition rates also exceeded 50%. Similarly, antioxidant assays (DPPH˙, ABTS˙⁺, and FRAP) confirmed stronger radical scavenging and reducing ability of the AgNPs compared to the extract. DFT calculations suggest that trans-ferulic acid and hesperidin interact with silver atoms through oxygen-containing functional groups, which likely contribute to nanoparticle formation and stabilization. Molecular docking results further showed favorable interactions between ferulic acid, hesperidin, and Ag complexes with key antioxidant and antibacterial target proteins, supporting the experimental findings. Overall, plant-mediated AgNPs appear promising for biomedical and biotechnological applications due to their antibacterial, antibiofilm, and antioxidant properties.