Benzofuran-isatin-imine hybrids tethered via different length alkyl linkers: Design, synthesis and in vitro evaluation of anti-tubercular and anti-bacterial activities as well as cytotoxicity.

Herein we report the design and synthesis of twenty-two novel benzofuran-isatin-imine hybrids 7a-v tethered through propylene, butylene, pentylene and hexylene, and for the evaluation of their in vitro anti-tubercular and anti-bacterial activities as well as cytotoxicity. All benzofuran-isatin-imine hybrids exhibited considerable in vitro anti-TB (MIC: <0.016-0.218 μg/mL and 0.062-14.15 μg/mL against drug-sensitive and MDR MTB, respectively) and anti-bacterial (MIC: 0.25-64 μg/mL and 0.06-16 μg/mL against Gram-positive and Gram-negative strains, respectively) activities. All of them also showed acceptable cytotoxicity towards VERO (CC: 8-128 μg/mL). The most active hybrid 7j (MIC: <0.016, 0.062 and 0.16 μg/mL, respectively) was >4.8 and ≥ 48 folds more potent than the first line anti-TB agents RIF and INH against both drug-sensitive MTB HRv and MDR-TB isolates, respectively. Moreover, hybrid 7j also demonstrated promising anti-bacterial activities with MIC values of ≤1 μg/mL against the majority of the tested Gram-negative and Gram-positive pathogens, which was comparable to vancomycin (MIC: 0.5-4 μg/mL) and CPFX (MIC: 0.125-8 μg/mL) against Gram-positive bacteria, but slightly less potent than CPFX (MIC: ≤0.03-0.5 μg/mL) against Gram-negative bacteria. The results indicated that benzofuran-isatin-imine hybrids could act as candidates for the development of anti-TB and anti-bacterial agents.