Synthesis, spectral analysis, antibacterial, antifungal, antioxidant and hemolytic activity studies of some new 2,5-disubstituted-1,3,4-oxadiazoles

Series of 1,3,4-oxadiazole derivatives (5a-5g and 5h, 5i) were synthesized and characterized by FT-IR, H-1 NMR, C-13 NMR and HR-MS spectral analysis. All the target compounds were screened for their in vitro antibacterial activity against two Gram-negative bacterial strains namely Escherichia coli (MTCC 405) and Salmonella typhi (MTCC 3224) and two Gram-positive bacterial strains namely Bacillus subtilis (MTCC 1790) and Bacillus megaterium (MTCC 1684) and antifungal activity against Aspergillus niger (MTCC 282), Rhizopus oryzae (MTCC 262), Penicillium chrysogenum (MTCC 974), and Candida albicans (MTCC 183) fungal strains. The synthesized compounds exhibited significant antibacterial and antifungal potential. Three compounds (5e, 5f and 5g) have shown higher antibacterial activity with very low MIC values comparable to streptomycin. According to the SAR study, the antibacterial efficacy can be intensified by substituting fluoro and methyl substituents at the para position in acid hydrazide. The synthesized compounds were also screened for % radical scavenging activity by OH and DPPH assay and found to be good antioxidant agents. Besides, the hemolytic study revealed that the synthesized 1,3,4-oxadiazoles possessed negligible cytotoxicity compared with the standard. (c) 2021 Elsevier B.V. All rights reserved.