Biological and Sensing Applications of a Few 1,3,4-Oxadiazole Based Donor-Acceptor Systems.

1,3,4-Oxadiazole pharmacophore is still considered a viable biologically active scaffold for the synthesis of more effectual and broad-spectrum antimicrobial agents. Therefore, the present study is based on five 1,3,4-oxadiazole target structures, viz., CAROT, CAROP, CARON (D-A-D-A systems) and NOPON and BOPOB (D-A-D-A-D systems) bearing various bioactive heterocyclic moieties relevant to potential biological activities. Three of the compounds, CARON, NOPON and BOPOB were assessed in-vitro for their efficacy as antimicrobial agents against gram positive (Staphylococcus aureus and Bacillus cereus) and gram negative (Escherichia coli and Klebsiella pneumonia) bacteria; and two fungi, Aspergillus niger and Candida albicans; also, as an anti-tuberculosis agent against Mycobacterium tuberculosis. Most of the tested compounds displayed promising antimicrobial activity, especially CARON which was then analyzed for the minimum inhibitory concentration (MIC) studies. Similarly, NOPON portrayed the highest anti-TB activity among the studied compounds. Consequently, to justify the detected anti-TB activity of these compounds and to recognize the binding mode and important interactions between the compounds and the ligand binding site of the potential target, these compounds were docked into the active binding site of cytochrome P450 CYP121 enzyme of Mycobacterium tuberculosis, 3G5H. The docking results were in good agreement with the result of in-vitro studies. In addition, all the five compounds were tested for their cell viability and have been investigated for cell labeling applications. To conclude, one of the target compounds, CAROT was used for the selective recognition of cyanide ion by 'turn-off' fluorescent sensing technique. The entire sensing activity was examined by spectrofluorometric method and MALDI spectral studies. The limit of detection obtained was 0.14 µM.