Microwave-assisted organic synthesis, antimycobacterial activity, structure–activity relationship and molecular docking studies of some novel indole-oxadiazole hybrids

Multidrug-resistant tuberculosis (MDR-TB) is a severe threat to mankind because most drugs are ineffective in inhibiting tubercular strains. Due to the increase of MDR-TB, many first and second-line drugs are ineffective against tubercular strains. To combat the resistance of currently accessible drugs, structural changes must be made on a regular basis. Thus, in the search for new antimycobacterial drugs, a series of 1-(2-(1<i>H</i>-indol-3-yl)-5-phenyl-1,3,4-oxadiazol-3(2<i>H</i>)-yl)-3-phenylprop-2-en-1-ones (5a-o) have been developed, synthesized, characterized, and screened for antimycobacterial activity. The synthetic approach includes imine generation and cyclization using both conventional and microwave methods to create hybrid molecules with indole and oxadiazole motifs. The set of synthesized compounds have demonstrated some promising activity against tubercular strains of <i>Mycobacterium tuberculosis</i> (ATCC 25177) and <i>M. bovis</i> (ATCC 35734). Compound 5l inhibited <i>M. bovis</i> strain 100% in 10 µg/mL concentration, while compound 5m inhibited <i>M. tuberculosis</i> strain 90.4% in 30 µg/mL concentration. Molecular docking study against mycobacterial enoyl reductase (InhA) could provide well-clustered solutions to the binding modes and affinity for these molecules as compound 5l showed glide score of −12.275 and glide energy of −54.937 kcal/mol.