Antibacterial and antiproliferative activity of novel 2-benzimidazolyl- and 2-benzothiazolyl-substituted benzo[ b ]thieno-2-carboxamides

Novel nitro ( 3a–3f )- and amino ( 4a–4f and 5a–5f )-substituted 2-benzimidazolyl and 2-benzothiazolyl benzo[ b ]thieno-2-carboxamides were designed and synthesized as potential antibacterial agents. The antibacterial activity of these compounds has been evaluated against Gram-positive ( Staphylococcus aureus and Enterococcus faecalis ) and Gram-negative bacteria ( Escherichia coli and Moraxella catarrhalis ). The most promising antibacterial activity was observed for the nitro- and amino-substituted benzimidazole derivatives 3a , 4a , 5a and 5b with MICs 2–8 g/mL . Additionally, compounds with inferior antibacterial activity were further tested for their antiproliferative activity in vitro against three human cancer cell lines. Amino-substituted benzothiazole hydrochloride salt 5d displayed the most pronounced and selective activity against the MCF-7 cell line with an IC_50 of 40 nM. Furthermore, DNA binding experiments of selected derivatives indicated that DNA cannot be considered as a primary biological target for this type of compounds. Graphical Abstract