Phytofabrication of Mono-Metallic Silver Nanoparticles: Chemical Characterization and Quantum Computational Analysis for Enhanced Antimicrobial Properties in Fresh Vegetable Preservation

The green synthesis of silver nanoparticles (AgNPs) using Lophira alata (LA) and Burkea africana (BA) extracts offers a sustainable approach for antimicrobial vegetable preservation. Phytochemicals like polyphenols and flavonoids act as reducing agents, with UV-vis spectroscopy confirming AgNP formation (peak at 420 nm). XRD revealed crystallite sizes of 13.66 nm (LA-AgNPs) and 8.78 nm (BA-AgNPs), while TEM showed spherical particles (10–50 nm). LA-AgNPs exhibited strong antibacterial activity, with inhibition zones of 14.45 mm (Staphylococcus aureus) and 13.55 mm (Pseudomonas aeruginosa). BA-AgNPs showed the lowest MIC against Bacillus subtilis (3.45 µg/mL vs. chloramphenicol’s 5.72 µg/mL) and superior bactericidal effects (MBC: 6.90 µg/mL vs. 11.44 µg/mL). Both AgNPs inhibited cellulase (90%) and pectinase (87%), crucial for extending vegetable shelf life. Quantum computational analysis revealed optimal energy gaps (LA-AgNPs: 0.88 eV; BA-AgNPs: 0.76 eV), indicating high reactivity. Non-covalent interaction (NCI) analysis confirmed stabilization via van der Waals forces and hydrogen bonding. Adsorption studies highlighted strong binding energies (−1.51 to −2.52 eV) for key phytocompounds (Lophirone, Betulinic acid, Fisetinidol), ensuring nanoparticle stability. These findings demonstrate the potential of LA- and BA-AgNPs as eco-friendly antimicrobial agents for food preservation.