Biogenic AgNPs from Leptadenia arborea: Integrated Antimicrobial, OmpF/Erg11 Docking, and Membrane-disruptive Mechanisms

Abstract

Plant-derived materials offer sustainable platforms for functional nanomaterial development; however, Leptadenia arborea remains poorly explored for silver nanoparticle (AgNP) synthesis, and quantitative approaches linking phytochemistry, antimicrobial efficacy, and cellular damage are limited. This study investigated L. arborea leaf extract as a reducing and stabilizing system for AgNP synthesis. HPLC identified chlorogenic acid (53.8 µg mL⁻¹) and gallic acid (53.3 µg mL⁻¹) as major phytochemicals. Replicated optimization experiments identified 1:50 extract dilution, 5 mM AgNO₃, 70 °C, and 2 mL extract as optimal conditions, producing a surface plasmon resonance peak at 435 nm. TEM revealed predominantly spherical AgNPs (12 to 24 nm), while XRD showed (111), (200), (220), and (311) reflections characteristic of crystalline face-centered cubic silver. AgNPs produced inhibition zones of 15 ± 0.7 mm against Escherichia coli and 30 ± 1.0 mm against Candida albicans, with an MIC of 0.117 µg mL⁻¹ against E. coli. As a key novelty, AEF enables normalized comparison with reference antimicrobials, while NBIP converts SEM-observed cellular damage into a quantitative index. This framework extends conventional inhibition-based assessment by integrating antimicrobial potency with cellular damage and provides a transferable approach for evaluating plant-derived antimicrobial nanomaterials.