Discovery of dual cation-π inhibitors of acetylcholinesterase: design, synthesis and biological evaluation

Abstract

Background: Alzheimer's disease (AD) is a widespread dementia-related disease affecting mankind worldwide. A cholinergic hypothesis is considered the most effective target for treating mild to moderate AD. Present study aims to identify new scaffolds for inhibiting acetylcholinesterase activity. Methods: To find Acetylcholinesterase (AChE) inhibitors, we computationally designed and chemically synthesized a series of cation-π inhibitors based on novel scaffolds that potentially block AChE. The cytotoxic effect of inhibitors were determined by MTT. AChE inhibition experiment was performed by Ellman and the Amplex red method in the SH-SY5Y cell line. Further, the experimental data on designed compounds corroborate with various computational studies that further elucidate the binding mode of interactions and binding affinity. Results: The inhibitors were designed to promote dual binding and were incorporated with groups that may facilitate any of the cation- π, hydrophobic and hydrogen-bonding interactions with the conserved and hot-spot residues in the binding site. The inhibitors possessing pyridine-N-methylated pyridinium group and thereby involved in cation- π interactions are highly active relative to the marketed drug Donepezil as well as the designed analogs that lack the group. In vitro enzymatic Ellman assay and Amplex red assay on SH-SY5Y cell line estimated IC50 of the designed compounds in nM range with one having binding affinity higher than Donepezil. Compounds exhibit no significant toxicity up to µM range. Conclusions: Compounds possessing methylidenecyclohexanone scaffolds, with characteristic dual-binding and involving strong cation-π interactions, serves as new leads for AChE and opens a new direction for drug discovery efforts.