Baharullah Khattak

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.

Pesticides are usually used to eliminate weeds and insects to improve crop quality and yield. The present study was undertaken to explore pesticides (Lambda cyhalotherin (LC) and Emamectin benzoate (EB)) related physiological, biochemical and ultrastructural changes in leaves of maize seedlings at different concentrations of LC and EB both singly (LC100, LC500, LC800, EB100, EB300, EB600 mg/L) and jointly (LC500 + EB300 mg/L) along with control. Germination percentage, root stem and leaf lengths increased at lower concentrations of both pesticides and significantly decreased with the increase in the external application of pesticides. At higher concentrations of LC and EB (i.e., LC800 and EB600 mg/L) the mean values of growth and biomass of maize leaves were lower than control. Also, decreases in photosynthetic pigments and ion concentration of Na1+, Ca2+ and K1+ were significant when the concentration of both pesticides increased. The melondialdehyde (MDA) contents decreased, while the amount of hydrogen peroxide (H2O2) production increased at higher doses in cases of single and joint applications. With the increase in their concentrations, the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were found to be pronouncedly enhanced as compared to control. Ultrastructural alterations in mesophyll cells of maize leaf were mostly found in chloroplast and nucleus. The present study revealed that short-term exposure of maize seedlings to pesticides (LC and EB) caused less stressful effects on maize due to the presence of active antioxidative metabolism, which indicates the resistant nature of maize toward these pesticides.