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Synthesis and antioxidant evaluation of thioether derivatives of thymol

Thymol is a monoterpene phenol which is found in significant amounts in the essential oils of thyme and oregano. The biological activities of thymol include antibacterial, antifungal, anticancer, antioxidant and insecticidal effects. The current study is focused on the synthesis and antioxidant studies of a series of sulfur containing heterocyclic derivatives of thymol, namely benzimidazole, benzoxazole, benzothiazole, amino thiadiazole, picolinic oxadiazole, nicotinic oxadiazole and isonicotinic oxadiazole. The synthesis of the thymol derivatives was achieved in three steps, with yields ranging from 46-96%. The compounds were characterized using NMR spectroscopy, and the antioxidant capacity for each derivative was measured using the cupric ion reducing antioxidant capacity (CUPRAC) assay method. The benzimidazole, picolinic oxadiazole, and amino thiadiazole derivatives showed stronger antioxidant capacity than thymol, ascorbic acid (vitamin C) and trolox, a derivative of vitamin E.