Synthesis and Biological Evaluation of Thymol Functionalized Oxadiazole thiol, Triazole thione and β-lactam Derivatives

In the present study, different derivatives of thymol (1) viz. hydrazide (2), oxadiazole thiol (3), triazole thione (4), hydrazones (5-7), and β-lactams (8-10) were synthesized. All synthesized compounds were identified and characterized using elemental analysis, UV-Visible, ¹H NMR, ¹³C NMR, and IR spectroscopic techniques. Synthesized thymol derivatives were evaluated for antifungal potential against phytopathogenic fungi Fusarium moniliforme, Rhizoctonia solani, and Dreschlera maydis of maize in comparison to recommended standards in terms of percent inhibition and ED50 values. Thymol was more effective as compared to its derivatives against all three tested fungi. Hydrazones (5-7) and β-lactams (8-10), having m-NO₂ substituted phenyl ring (6, 9), were less effective as compared to o-NO₂ and p-NO₂ analogs against F. moniliforme and R. solani, however, the reverse trend was observed against D. maydis. Thymol and its derivatives were also tested for insecticidal activity against stored grain (chickpea) insect Callosobruchus chinensis and various parameters viz. egg laying, adult emergence, and grain damage were recorded and compared. Compounds having oxadiazole thiol (3) and triazole thione (4) moiety showed promising effects against insect C. chinensis.