An Integrated Assessment of Zinc Oxide Nanoparticles in Salinity-Stressed Zea mays: From Antimicrobial Bioactivity to Molecular Docking Simulations

Salinity stress adversely affects plant growth, yield, and productivity. It requires an investigation of ameliorative techniques, for example, spraying synthesized nanoparticles such as zinc oxide nanoparticles (ZnOnps). This current research studied the impact of sodium chloride as a stressor (150 mM NaCl) and the application of ZnOnps (2 g L⁻¹) on some biochemical properties of maize (Zea mays) leaves. The experiment involved examining some mineral concentrations (Na, K, Mg, Zn, Cu, Mn), fatty acid profile, and the antimicrobial (antibacterial and antifungal) properties of aqueous and diethyl ether maize leaf extracts, supported by molecular docking studies of the 17 previously determined phenolic compounds against DNA gyrase and alpha-L-fucosidase enzymes. Applying ZnOnps markedly decreased sodium concentrations from 5.8 to 1.9 mg g⁻¹ dry weight (DW) and established ion balance. ZnOnps also reduced γ-linolenic acid levels to 60% under stress, returning them to normal (34%), while increasing palmitic acid to 30%. Determining the antimicrobial activities indicated that extracts from plants sprayed with ZnOnps exhibited enhanced antimicrobial activity, as evidenced by the lowest minimum inhibitory concentrations against bacterial and fungal strains, including Salmonella typhi and Aspergillus flavus. The computational molecular docking confirmed the antimicrobial findings, with the compound apigenin-7-glucoside, which exhibited the highest binding affinity scores for antibacterial (−7.4 kcal/mol), and the compound chlorogenic acid as antifungal (−7.2 kcal/mol) against the enzyme targets. Thus, ZnOnps can be considered an efficient strategy for mitigating salinity stress in maize plants while elevating the antimicrobial activity and stability of variant secondary compounds.