Design, synthesis and mode of action of novel 2-(4-aminophenyl)benzothiazole derivatives bearing semicarbazone and thiosemicarbazone moiety as potent antimicrobial agents

A novel series of substituted benzothiazoles, bearing semicarbazone and thiosemicarbazone moieties, was designed, synthesized and evaluated for their antimicrobial activity and possible mode of action. Structures of the synthesized compounds were elucidated by H-1 NMR, C-13 NMR, IR and Mass spectral data. The results revealed that compounds SC06, SC09, TS05 and TS07 have potent antibacterial activity against both Gram-positive and Gram-negative strains. Compound TS05 displayed most potent activity with MIC values of 3.91, 7.81 and 1.56 A mu g/ml against S. aureus, E. coli and P. aeruginosa, respectively. The results from cytoplasmic membrane permeabilization assay, FACS study as well as DNA-binding assays, evaluated against clinically relevant pathogens S. aureus and E. coli, suggest membrane perturbing as well as intracellular mode of action of this class of compounds. In addition, hemolytic activity of the compounds was measured which indicated their low cytotoxicity.