2-amino-6-ethoxy-4-arylpyridine-3,5-dicarbonitrile Scaffolds as potential acetylcholinesterase and butyrylcholinesterase inhibitors

Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes are of prime importance for treating Alzheimer's disease (AD). Apart from many organic scaffolds, pyridine-based compounds have previously been reported as potential alpha-glucosidase inhibitors. The current study reports a series of pyridine-based synthetic molecules for their acetylcholinesterase AChE and butyrylcholinesterase BChE inhibitory potential assessed via in vitro, kinetics, and in silico studies. For this purpose, 2-amino-6-ethoxy-4-arylpyridine-3,5-dicarbonitrile analogs 1-23 were synthesized by using a two-step reaction scheme. In the first step, different aryl aldehydes were treated with malononitrile to afford the 2-benzylidenemalononitrile in the presence of catalyst ammonium acetate. In the next step, 2-benzylidenemalononitrile intermediates were reacted again with malononitrile, catalyzed by potassium hydroxide, to synthesize a range of functionalized pyridine scaffolds in good yields. Compounds were subjected to in vitro screening against AChE and BChE enzymes. Several derivatives, including 2, 3, 11, 14-16, 19, 20, and 22, showed many folds of increased inhibitory potential and binding affinity in the ranges of Ki = 1.62 +/- 0.13 nM to 15.84 +/- 0.10 nM for AChE and Ki = 1.35 +/- 0.31 nM to 13.52 +/- 0.61 nM for BChE, as compared to the standard tacrine Ki = 53.31 +/- 11.32 nM for AChE, and Ki = 58.16 +/- 7.24 nM for BChE. Further, molecular docking studies deduced key interactions between the ligands (compounds) and the active pocket of enzymes. The current research study has identified several potential AChE and BChE inhibitors that may serve as lead candidates after targeted advanced research for exploring anti-Alzheimer agents.