Substituted-1,3,4-oxadiazole Indole Derivatives: Design, Synthesis, Characterization, and Evaluation of the Antimicrobial and Anti-Inflammatory Activities

In view of the significant biological potency of indole derivatives and 1,3,4-oxadiazoles, in the present work we synthesized a new series of indole-based substituted 1,3,4-oxadiazole derivatives, specifically 1-[5-(1H-indol-5-yl)-2-substituted-1,3,4-oxadiazol-3(2H)-yl]ethenones from 1H-indole-5-carboxylic acid through a sequence of reactions. All the synthesized compounds were evaluated for their antimicrobial and ant-inflammatory activities. The results of the antimicrobial assay showed that most of the products exhibited promising activity against the tested bacterial strains, especially P. aeruginosa (ATCC27853) with MIC 6.25 μg/mL, whereas very few compounds showed a high antifungal activity with MICs ranging from 6.25 to 50.0 μg/mL. All the synthesized compounds showed a low to moderate antiinflammatory activity with the albumin denaturation inhibition activity of < 66%, which is lower than that of the standard drug diclofenac (85.5%). Overall, the biological testing showed that the indole-based substituted 1,3,4-oxadiazole derivatives act as potent antibacterial rather than anti-inflammatory agents, and their activity can be enhanced by the introduction of an appropriate pharmacophoric substituent in the 1,3,4-oxadiazole motif.