Eco-friendly synthesis of copper oxide nanoparticles using Myrtus communis L . leaf extract: characterization, antimicrobial activity, and in vivo toxicity evaluation

This study aimed to synthesize CuO-NPs using Myrtus communis leaf extract via a green synthesis approach and to evaluate their antimicrobial and in vivo toxicity effects. CuO-NPs were synthesized using Myrtus communis leaves as a reducing and stabilizing agent and characterized using UV–Visible spectroscopy, FTIR, XRD, SEM, and EDX. Antibacterial and antifungal activities were evaluated against selected pathogenic microorganisms, and in vivo toxicity was assessed in BALB/c mice via histopathological examination. Characterization confirmed the formation of crystalline CuO-NPs with nanoscale dimensions. The nanoparticles demonstrated significant antibacterial activity against Gram-positive and Gram-negative bacteria, with Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli being the most susceptible species (MICs: 3.125 µg/100 µL, 12.5 µg/100 µL, and 12.5 µg/100 µL, respectively). Antifungal activity was evidenced by reduced colony growth and morphological alterations in fungal species. In Penicillium sp., colony diameter decreased from 77.1 mm in controls to 28.5 mm following treatment. Similar effects were observed in Aspergillus niger and Aspergillus fumigatus. Lower doses of CuO-NPs were well tolerated, whereas higher doses caused histopathological changes in the kidney and intestine. Green-synthesized CuO-NPs from Myrtus communis exhibited potent antibacterial and antifungal activities, with acceptable biocompatibility at lower concentrations, highlighting their potential for biomedical applications.