Synthesis of indole-2-carbohydrazides and 2-(indol-2-yl)-1,3,4-oxadiazoles as antioxidants and their acetylcholinesterase inhibition properties

A range of novel 4,6-dimethoxy-1H-indole-2-carbohydrazides was prepared starting from methyl 4,6-dimethoxy-1H-indole-2-carboxylate which underwent cyclodehydration to generate the corresponding 2-(indol-2-yl)-1,3,4-oxadiazole scaffolds in the presence of N,N-diisopropylethylamine and p-toluenesulfonyl chloride in acetonitrile. All novel compounds were fully characterized by 1H NMR, 13C NMR, FT-IR, and high-resolution mass spectroscopic data. Biological importance of the designated compounds was identified by employing three different antioxidant property determination assays, namely DPPH free radical scavenging, ABTS cationic radical decolarization, and cupric reducing antioxidant capacity (CUPRAC). The anticholinesterase properties were also evaluated by the acetylcholinesterase and butyrylcholinesterase enzyme inhibition assays. According to the results, the indole compounds possessing carbohydrazide functionality were found to be more promising antioxidant targets than the 2-(indol-2-yl)-1,3,4-oxadiazole systems. Nʹ-Benzoyl-4,6-dimethoxy-1H-indole-2-carbohydrazide, a member of the dimethoxyindole-2-carbohydrazide group, demonstrated a better inhibition performance than the standards. Additionally, extremely important results were obtained in the anticholinesterase enzyme inhibition assays in the case of 2-(indol-2-yl)-1,3,4-oxadiazole derivatives.