Antimicrobial Evaluation and Docking Study of Some 2-Aryl-5-(Pyridin-3-Yl)-1,3,4-Oxadiazole Derivatives

1,3,4-oxadiazoles are interesting compounds because of their valuable biological effects. A new series of some 2-aryl-5-(pyridin-3-yl)-1,3,4-oxadiazole derivatives (3a-3h) were synthesized and screened for their antimicrobial activity. These compounds (3a-3h) were prepared from the reaction of nicotinic acid with ethyl alcohol converted into ethyl nicotinate (1) by esterification. Compound (1) is converted to nicotinohydrazide (2) by treating with hydrazine hydrate. Compound 2 is converted to compounds 3a-3h by treating with appropriate aromatic carboxylic acids in the presence of POCl3. Confirm of structures of the synthesized compounds by using IR, (HNMR)-H-1, and MS spectroscopy. All the title compounds were tested for in vitro antibacterial activity against Staphylococcus aureus, Bacillus subtilis (Gram-positive), Pseudomonas aeruginosa, Escherichia coli (Gram-positive) bacteria, and antifungal activity against Candida albicans and Aspergillus niger. Most of the compounds showed good activity against all the organisms. Compounds 3b, 3d, 3e, 3g, 3j, and 31 showed the highest activity against bacteria strains when compared to the standard ciprofloxacin. Compounds 3b, 3d, 3e, 3g, 3j, 3k, and 3l were showed better antifungal activity against fungal strains as compared to the standard drug griseofulvina.