Synthesis and biological evaluation of 2-mercapto-1,3-benzothiazole derivatives with potential antimicrobial activity

The enhancement of bacterial resistance of pathogens to currently available antibiotics constitutes a serious public health threat. So, intensive efforts are underway worldwide to develop new antimicrobial agents. To identify compounds with a potent antimicrobial profile, we designed and synthesized low molecular weight 2-mercaptobenzothiazole derivatives 2a-2l and 3a-3l. Both series were screened for in-vitro antibacterial activity against the representative panel of Gram-positive and Gram-negative bacteria strains. The biological screening identified compounds 2e and 2l as the most active ones showing an interesting antibacterial activity with MIC values of 3.12 microg/mL against Staphylococcus aureus and 25 microg/mL against Escherichia coli, respectively. The replacement of the S-H by the S-Bn moiety resulted in considerable loss of the antibacterial action of the 3a-3l series. The antibiotic action of compounds 2e and 2l was also investigated by testing their activity against some clinical isolates with different antimicrobial resistance profile. Moreover, the involvement of the NorA efflux pump in the antibacterial activity of our molecules was evaluated. Finally, in this paper, we also describe the cytotoxic activity of the most interesting compounds by MTS assay against HeLa and MRC-5 cell lines.