Synthesis, antibacterial, antioxidant, and molecular docking studies of 6-methylpyrimidin-4(3H)-one and oxo-1,2,4-triazolo[4,3-a]pyrimidine derivatives

A series of 6-methylpyrimidin-4(3H)-one and oxo-1,2,4-triazolo[4,3-a]pyrimidine derivatives (1-18) was designed to meet the urgent need for novel antibacterial and antioxidant agents. The in vitro antibacterial activity revealed that most of the compounds exhibited a good inhibitory effect on Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria with MIC values in the range of 55-200 mu g/mL for E. coli and 125-700 mu g/mL for S. aureus. (E)-2-(2-(4-methoxybenzylidene)hydrazinyl)-6-methylpyrimidin-4(3H)-one (8) was the most active compound (MIC = 55 and 125 mu g/mL against E. coli and S. aureus, respectively). All compounds exhibited antioxidant activity ranged from weak to moderate and high. The obtained findings revealed that compounds 3, 5, 6, 9, 16, and 18 have superiority among all compounds, demonstrating the highest capacity to deplete DPPH (1,1-diphenyl-2-picrylhydrazyl), compared to alpha-tocopherol, as a standard antioxidant agent. Surprisingly, compound 3 (2-hydrazinyl-6-methylpyrimidin-4(3H)-one) showed significantly higher antioxidant activity (EC50 = 2.12 mu g/mL) than alpha-tocopherol (EC50 = 9.16 mu g/mL). Molecular docking, drug-likeness data, physicochemical properties, and ADMET parameters of the compounds were in silico computed. The derivatives presented good properties for Lipinski's parameters, poor solubility in the aqueous medium (Log S of -1.27 to -5.45), and PSA <= 140, indicating good permeability in biological membranes and gastrointestinal absorption. Molecular docking to the active sites of penicillin-binding protein and NADPH oxidase revealed that most compounds displayed minimal binding energy and have a good affinity toward the active pocket. (C) 2021 Elsevier B.V. All rights reserved.