Design, Synthesis and Antifungal Evaluation of Novel Substituted

Objective: The purpose of this research is to evaluate the antifungal activity of synthesized conjugates of thiophene with 1, 3, 4-oxadiazoles and 1, 3, 4-thiadiazoles using in vitro methods. Methods: The series of (IVa-e) and (Va-e) compounds were synthesized from thiosemicarbazide (IIIa-e) series by treating with iodine-sodium hydroxide mixture and by phosphoric acid cyclization respectively. Thiosemicarbazides (IIIa-e) were prepared by the reaction of 2–amino-4, 5, 6, 7tetrahydro-benzo[b]thiophene-3-carbohydrazide (II) with substituted isothiocyanates. Carbohydrazide (II) was synthesized by the reaction of hydrazine hydrate with ethyl 2–amino-4, 5, 6, 7-tetrahydrobenzeno[b]thiophene-3-carboxylate (I), which was prepared by one pot synthesis method. Finally, the synthesized compound series was characterized by physicochemical and spectral data (IR, NMR and Mass) and evaluated for in vitro antifungal activity against Candida albicans and Aspergillus niger using disc diffusion method. The percentage inhibition was calculated with reference to the standard drug. Results: The structures of the synthesized conjugates of thiophene with 1, 3, 4-oxadiazoles and 1, 3, 4–thiadiazoles were confirmed by IR, NMR, and Mass spectroscopic techniques. The results of bioassay were indicated that some synthesized compounds IVd, IVe, Vd, and Ve exhibited moderate antifungal activities against Candida albicans and Aspergillus niger; whereas compounds IVb, IVc, Vb, and Vc showed prominent antifungal activities when compared to standard drug, Fluconazole. Conclusion: Present study demonstrates the synthesis of conjugates of thiophene with 1, 3, 4-oxadiazoles and 1, 3, 4–thiadiazoles. These compounds were evaluated for in vitro antifungal activity against Candida albicans and Aspergillus niger using disc diffusion method. The compounds IVd, IVe, Vd, and Ve exhibited moderate antifungal activities, whereas compounds IVb, IVc, Vb, and Vc showed prominent antifungal activities.