Introduction: Escalating antimicrobial resistance necessitates alternatives or adjuvants to conventional antibiotics, positioning green-synthesized metal nanoparticles as biocompatible, eco-friendly candidates with broad-spectrum activity. Rosemary (Rosmarinus officinalis) extract provides phenolic and flavonoid reducers/capping agents—carnosic acid, rosmarinic acid, caffeic acid, apigenin, and luteolin—that enable nanoparticle formation while enhancing stability and biological functionality.
Methods: Green synthesis employs aqueous or alcoholic rosemary extracts added to metal salt solutions (e.g., AgNO3), with parameters such as pH, temperature, and reactant concentrations tuned to control nucleation, growth, size, and shape. Standard characterization confirms nanoparticle formation and properties via UV–Vis spectroscopy, SEM/TEM imaging, XRD crystallinity, and FTIR surface chemistry, while phytochemicals serve dually as reducing and capping agents; the approach generalizes to selenium by reducing Se⁴⁺ to Se⁰.
Results: Rosemary-mediated nanoparticles are typically spherical and 20–50 nm, maximizing surface-to-volume ratio and contact with microbial envelopes; mechanisms include reactive oxygen species generation, membrane disruption with permeability/ion imbalance, and metabolic interference. Broad-spectrum efficacy spans Gram-positive and Gram-negative bacteria, with inhibition zones reported up to 32 mm and low MIC/MBC values of 3.13–6.25 μg/mL against Staphylococcus aureus, Escherichia coli, Listeria monocytogenes, and Pseudomonas aeruginosa, including activity against MRSA and synergy with metal oxides/antibiotics. Antifungal and antibiofilm effects include Candida albicans growth inhibition and suppression of Klebsiella pneumoniae adhesin expression, while rosemary extract also demonstrates antiviral activity against HSV-1/HSV-2 and pre-entry virucidal effects against Zika virus; nanoencapsulation (e.g., zein, chitosan) improves stability and controlled release.
Conclusion: Rosemary-enabled green nanomaterials offer a cost-effective, scalable, and environmentally compatible pathway to antimicrobial agents and adjuvants capable of complementing or reducing reliance on traditional antibiotics. Their mechanistic breadth, favorable size range, and formulation versatility support translational potential against drug-resistant infections across bacterial, fungal/biofilm, and select viral targets.
Keywords: Green synthesis; Rosemary extract; Silver nanoparticles; Antimicrobial resistance