Synthesis and biological evaluation of novel hydrazone derivatives for the treatment of Alzheimer's disease

Abstract

In recent years, Alzheimer's disease has emerged as a silent epidemic neurodegenerative disorder. Due to its complex pathophysiology, there has been significant scientific interest in developing effective treatments that go beyond symptomatic relief. The main aim is to improve patients' quality of life and lower the death rate associated with Alzheimer's disease. Since this has not yet been achieved, continued research on Alzheimer's disease remains a global priority. In this study, a total of 27 hybrid molecules (D1a–D1i, D2a–D2i, and D3a–D3i) were designed based on the molecular scaffold of donepezil, a well-known acetylcholinesterase inhibitor (AChEI). These hybrids incorporate dihydrothiazolyl hydrazone and phenyl piperidine moieties. All compounds were synthesized and characterized using IR, NMR, and HRMS spectroscopy, and subsequently evaluated for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition using the in vitro Ellman method. Evaluation of biological activity revealed that compound D1f exhibited the highest inhibitory activity against the AChE enzyme, with an IC₅₀ of (0.039 ± 0.001 Mm). In contrast, none of the compounds showed significant inhibitory activity against the BChE enzyme. Cytotoxicity testing of compound D1f on NIH3T3 fibroblast cells demonstrated non-cytotoxic effects (IC₅₀ = 3.324 ± 0.155 µM) and the highest selectivity index (SI = 85.231), respectively. Molecular docking and molecular dynamics simulations verified the stable binding affinity and favorable interactions of compound D1f within the active site of acetylcholinesterase (AChE). The results further demonstrated that the AChE enzyme preserved its structural integrity and compactness throughout its interaction with D1f. Collectively, these observations highlight D1f as a promising lead molecule for subsequent optimization and development of novel anti-Alzheimer's therapeutic agents.