Design and synthesis of novel coumarin derivatives as potential acetylcholinesterase inhibitors for Alzheimer's disease.

Twenty novel 7-benzyloxycoumarin based compounds were synthesized with a variety of bioactive chemical fragments. The synthesized compounds showed remarkable acetylcholinesterase (AChE) inhibitory activity. In vitro assay revealed that compounds 7-benzyloxy-4-{[(4-phenylthiazol-2(3H)-ylidene)hydrazono]methyl}-2H-chromen-2-one (5b, IC= 0.451μM), 7-benzyloxy-4-({[4-(4-methoxyphenyl)thiazol-2(3H)-ylidene]hydrazono}methyl)-2H-chromen-2-one (5d, IC= 0.625μM), 5-amino-1-[2-(7-benzyloxy-2-oxo-2H-chromen-4-yl)acetyl]-1H-pyrazole-4-carbonitrile (13c, IC= 0.466μM), 2-(7-benzyloxy-2-oxo-2H-chromen-4-yl)-N-(2-methylimino-4-phenylthiazol-3(2H)-yl)acetamide (16a, IC= 0.500μM) and 2-(7-benzyloxy-2-oxo-2H-chromen-4-yl)-N-[4-(4-methoxyphenyl)-2-methyliminothiazol-3(2H)-yl]acetamide (16b, IC= 0.590μM) exhibited promising AChE inhibitory activity even better than donepezil (IC= 0.711μM). Kinetic study for compound 5b implied mixed type inhibitor which could bind peripheral anionic site (PAS) and catalytic active site (CAS) of AChE enzyme. In addition, in vivo evaluation of compounds 5b, 13c and 16a confirmed significant memory improvement in scopolamine-induced impairment model in tested mice. Furthermore, in silico studies were performed on the synthesized compounds which included molecular docking study at the active site of recombinant human acetylcholinesterase enzyme (rhAChE) as well as prediction of ADMET and other physicochemical parameters. A correlation between the docking results and IC of tested compounds was routinely observed and shared similar binding pattern to the co-crystallized ligand donepezil.