Synthesis, characterization, in silico molecular docking, and antibacterial activities of some new nitrogen-heterocyclic analogues based on a p-phenolic unit.

Nitrogen-containing heterocycles have shown pharmacological properties against various diseases. Herein, in our study, flavoHB enzyme is a highly promising well-validated target for identification of antibacterial inhibitors using in silico and in vitro techniques. To identify a new class of antimicrobial agents, N-(4-hydroxyphenyl)-3-oxobutanamide was utilized as a precursor in the synthesis of several nitrogen-based heterocycles (pyridine, pyrimidine, and pyrazole) attached to p-phenolic substrates 2-8. Treatment of 3-oxobutanimide 1 with malononitrile and/or ethyl cyanoacetate in ethanolic piperidine afforded the pyridinone analogues 2a,b. On the other hand, treatment of 1 with arylidene cyanothioacetamide furnished the pyridinthione derivative 3. The reaction of starting material 1 with salicylaldehyde and/or dimethyl formamide dimethyl acetal (DMF-DMA) yielded the pyridinones 4 and 5, respectively. Reaction of 1 with terephthalaldehyde and urea or thiourea gave bis structures 6a,b. The reaction of compound 1 with ethyl isothiocyanate and hydrazine hydrate afforded pyrimidine and pyrazole derivatives 7 and 8, respectively. The structures of newly prepared compounds 2-8 were elucidated using elemental data and spectral analyses such as IR, 1H NMR, 13C NMR, and MS. In addition, an in-house nitrogen-containing heterocycle analogues library 2-8 was examined and screened in vitro for their antibacterial effects against Gram-negative bacteria, Escherichia coli and Gram-positive bacteria, Staphylococcus haemolyticus, Kocuria kristinae, Enterococcus casseliflavus, and Bacillus cereus. Compounds 6a and 6b have also shown the highest antibacterial activity against all types of bacteria strains tested except Kocuria kristinae. Further, the molecular docking study of the newly prepared compounds with the target enzyme flavohemoglobin (flavoHB) was undertaken to explore their potential inhibitory activities. The results of the docking study indicated that compounds 6a and 6b have exerted the highest docking scores against the active site of flavoHB. As a result, the in vitro and molecular docking study findings suggested that the compounds 6a and 6b (with pyrimidine moiety, amide linkage, and phenolic substrate) might be potent bacterial flavohemoglobin (flavoHB) inhibitors and they could set a promising starting point for future design of antibacterial agents.

Eco-Friendly Synthesis, Biological Evaluation, and In Silico Molecular Docking Approach of Some New Quinoline Derivatives as Potential Antioxidant and Antibacterial Agents.

A new series of quinoline derivatives 5-12 were efficiently synthesized via one-pot multicomponent reaction (MCR) of resorcinol, aromatic aldehydes, ß-ketoesters, and aliphatic/aromatic amines under solvent-free conditions. All products were obtained in excellent yields, pure at low-cost processing, and short time. The structures of all compounds were characterized by means of spectral and elemental analyses. In addition, all the synthesized compounds 5-12 were in vitro screened for their antioxidant and antibacterial activity. Moreover, in silico molecular docking studies of the new quinoline derivatives with the target enzymes, human NAD (P)H dehydrogenase (quinone 1) and DNA gyrase, were achieved to endorse their binding affinities and to understand ligand-enzyme possible intermolecular interactions. Compound 9 displayed promising antioxidant and antibacterial activity, as well as it was found to have the highest negative binding energy of -9.1 and -9.3 kcal/mol for human NAD (P)H dehydrogenase (quinone 1) and DNA gyrase, respectively. Further, it complied with the Lipinski's rule of five, Veber, and Ghose. Therefore, the quinoline analogue 9 could be promising chemical scaffold for the development of future drug candidates as antioxidant and antibacterial agents.