Design, synthesis, molecular docking, and spectral studies of new class of carbazolyl polyhydroquinoline derivatives as promising antibacterial agents with noncytotoxicity towards human mononuclear cells from peripheral blood

Abstract In the present study, we report the design and eco‐benign synthesis of new class of carbazolyl‐1,4‐dihydropyridine (1,4‐CDHP) and carbazolyl‐1,8‐dioxodecahydroacridine (CAD) derivatives via a three‐component coupling reaction of substituted carbazole aldehydes, ethyl acetoacetate/dimedone, and ammonium acetate under solvent‐free conditions at 112°C to 115°C. We also report an efficient one‐pot synthesis of new class of carbazolyl polyhydroquinoline (CPQ) derivatives via a four‐component coupling reaction of substituted ethyl acetoacetate, dimedone, ammonium acetate, and carbazole aldehydes in acetonitrile/water medium (3:1) at 73°C to 75°C in moderate yields. All the products were thoroughly characterized by 1 H NMR, 13 C NMR, Fourier transform infrared (FTIR), mass spectral, and CHN analysis. The synthesized heterocyclic compounds were evaluated for their in vitro antibacterial activity against pathogenic strains of both Gram‐negative and Gram‐positive bacteria. Minimum inhibitory concentration (MIC) of the active compounds was evaluated by macrodilution method. The CPQ derivative ( 8a ) displayed superior antibacterial activity against Escherichia coli , Pseudomonas aeruginosa , and Salmonella typhi with the MIC values of 16.0 to 32.0 μg/mL in comparison with the reference drug. The mechanism of antibacterial action of the CPQ derivatives was investigated via scanning electron microscope (SEM) studies. The molecular docking studies indicate that the CPQ derivative ( 8a ) binds to the cell wall protein of E coli and P aeruginosa by formation of hydrogen bonds with amino acid residues (TYR328 and GLU249) of the bacterial cell wall protein. The 1,4‐CDHP, CAD, and CPQ derivatives were either noncytotoxic or exhibited minimal cytotoxicity towards human mononuclear cells from peripheral blood. All the products were evaluated for Lipinski rule of five (RO5) and were found to have good oral bioavailability.