Eco-Friendly Synthesis of Magnesium Oxide Nanoparticles Using Citrullus colocynthis and their Synergistic Antimicrobial Activity against Drug-Resistant Pathogens

The escalating threat of antimicrobial resistance (AMR) necessitates innovative therapeutic approaches. This study reports the green synthesis of magnesium oxide nanoparticles (MgO-NPs)using Citrullus colocynthis extract, a medicinal plant rich in bioactive compounds, as a sustainable alternative to conventional antibiotics. The synthesized MgO-NPs were characterized by UV-Vis spectroscopy (absorption peak at 250 nm), XRD (cubic crystalline structure, 15–25 nm size), SEM-EDX (agglomerated spherical morphology, Mg/O ratio 2.6:1), and FTIR (Mg-O vibration at 860 cm⁻¹). The nanoparticles exhibited potent, dose-dependent antibacterial activity against multidrug-resistant (MDR) Staphylococcus aureus (MIC: 35.3 µg/ml; MBC: 97.1 µg/ml) and Escherichia coli (MIC: 47.5 µg/ml; MBC: 105.5 µg/ml), with a bactericidal mode of action (MBC/MIC ≤ 4). Remarkably, MgO-NPs restored susceptibility to β-lactams antibiotics (ceftazidime and penicillin) in resistant strains, demonstrating synergistic effects. Antifungal activity of MgO-NPs against Candida albicans (17.3±0.7 mm) and Aspergillus niger (14.4±0.8 mm) at a concentration of 10 mg/ml was also observed. Phytochemical analysis revealed solvent-dependent bioactive constituents in C. colocynthis , with aqueous extracts rich in tannins/phenolics and methanolic extracts in flavonoids/terpenoids. This is the first report demonstrating restoration of antibiotic susceptibility by MgO-NPs synthesized from C. colocynthis extract.