The rising prevalence of multidrug-resistant (MDR) pathogens has heightened the need for sustainable, high-potency biocides. This work describes an aqueous root extract-based synergistic hybrid approach for green synthesis of silver nanoparticles (AgNPs) from two endemic Iranian species, Ferula assa-foetida and Ferula persica. Here, we established a precise morphological control framework using sodium citrate (NaC) as a co-reductant, in which increasing the citrate ratio effectively adjusted nanoparticle dimensions from 129 to 42 nm. UV-Vis, XRD, FESEM, and DLS were used to comprehensively characterize the formation of crystalline silver cores encapsulated within a robust sulfur-rich biomolecular corona. FTIR and EDS analysis confirmed a phytochemical-specific silver-sulfur (Ag-S) interface. The F. persica-mediated nanoparticles exhibited excellent colloidal stability, with zeta potential values ranging from -40 to -60 mV.
In antimicrobial assays, biogenic AgNPs showed significantly improved inhibitory profiles compared to chemically synthesized AgNPs. The Per/NaC 1/10 variant was found to be the most effective candidate with a remarkable Minimum Inhibitory Concentration (MIC) of 1 µg/mL against Staphylococcus aureus and 10 µg/mL against other bacterial strains. The nanoparticles exhibited broad-spectrum antibacterial activity; however, relative resistance to Candida albicans was observed, underscoring the influence of cell wall architecture on nano-bio interactions. The results highlight the importance of Ferula species as effective bio-templates for nanomanufacturing and provide a standardized route for developing next-generation biocompatible antimicrobial agents from endemic flora.