Eco-Friendly Synthesis of Magnesium Oxide Nanoparticles Using Citrullus colocynthis and their Synergistic...

The escalating threat of antimicrobial resistance (AMR) necessitates the development of 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 ± 2.1 µg/ml (0.0353 ± 0.0021 mg/ml); MBC: 97.1 ± 3.5 µg/ml (0.0971 ± 0.0035 mg/ml)] and Escherichia coli [MIC: 47.5 ± 4.2 µg/ml (0.0475 ± 0.0042 mg/ml); MBC: 105.5 ± 6.8 µg/ml (0.1055 ± 0.0068 mg/ml)], with a bactericidal mode of action (MBC/MIC ≤ 4). Remarkably, MgO-NPs restored susceptibility to β-lactam 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 rich in flavonoids/terpenoids. This is the first report demonstrating the restoration of antibiotic susceptibility by MgO-NPs synthesized from C. colocynthis extract.