Synthesis and antioxidant properties of novel thiosemicarbazide derivatives

Abstract

Novel derivatives of thiosemicarbazide were synthesized and evaluated for their antioxidant properties. Starting from readily available pyridine-2,5-dicarboxylic acid the title compounds were prepared. The reaction of carboxylic acid with absolute ethanol afforded the corresponding diethyl pyridine-2,5-dicarboxylate. The reaction of compound 1 with hydrazine hydrate good yielded pyridine-2,5-dicarbohydrazide. Refluxing compound 2 with alkyl/aryl isothiocyanate for 3-8 h afforded 1,4-disubstituted thiosemicarbazides in good yield (75-90%). The final compounds showed very high activity (88.16-71.34%) against 2,2-diphenyl-1-picrylhydrazyl free radical at the concentration of 25 μg/mL while the others showed lower activity.