Synthesis, in-vitro and in-silico antibacterial and computational studies of selected thiosemicarbazone-benzaldehyde derivatives as potential antibiotics

Abstract

Three new Schiff bases, (Z)-2-(4-(dimethylamino)benzylidene)-N-methylhydrazinecarbothioamide (PDM), (Z)-2-(2-hydroxy-5-nitrobenzylidene)-N-methylhydrazinecarbothioamide (5NS) and (Z)-2-(4-cyanobenzylidene)-N-methylhydrazinecarbothioamide (4CN) of thiosemicarbazone-benzaldehyde derivatives were synthesized by condensation reaction. These compounds were formed from the reaction of 4-methyl-3-thiosemicarbazide with p-dimethylaminobenzaldehyde, 5-nitrosalicylaldehyde and 4-formylbenzonitrile respectively. The molecules synthesized were screened against bacterial isolates; Gram-positive (Staphylococcus aureus and Bacillus cereus), and Gram-negative (Klebsiella pnuemoniae and Pseudomonas aeruginosa) bacteria using agar well diffusion technique, supported by molecular docking and theoretical analysis through computational approach adopting a coupled DFT-B3LYP and 6-31G(d) basis set. The in-vitro antibacterial studies proofed that the compounds have a broad-spectrum antibacterial activity against the bacterial isolates while 5NS (21.0 mm) and PDMA (9.5 mm) have higher antibacterial activities than the standard drug, streptomycin against Staphylococcus aureus (16.5 mm) and Pseudomonas aeruginosa (9.0 mm) respectively. Theoretical studies and molecular docking established the fact that these Schiff bases could be explored further as bioactive compounds against bacterial infections and also as corrosion inhibitors of metals in the oil and gas industry. Graphical abstract