Design, synthesis and biological evaluation of new carbazole-coumarin hybrids as dual binding site inhibitors of acetylcholinesterase

Twelve carbazole-coumarin hybrids were synthesized and biologically evaluated as dual binding site acetylcholinesterase inhibitors. The structures of the carbazole-coumarin hybrids were confirmed by IR, NMR, HRMS and single-crystal X-ray diffraction studies. The compound 3j had the crystal system of triclinic and the space group of P-1. The cholinesterase inhibitory activity of synthesized compounds was measured using colorimetric Ellman's method. Compound 3h exhibited good acetylcholinesterase (AChE) inhibitory activity (IC 50 value of 6.72 μ M) and a high selectivity over butyrylcholinesterase (BuChE). Compound 3k showed the best BuChE inhibitory activity with the IC 50 of 0.50 μM. The SAR studies revealed that the linker length played a crucial role in determining AChE inhibitory activity and the structure of the coumarin moieties affected the BuChE-inhibition activities of the hybrids. Molecular docking study of compound 3h indicated that it interacts with the crucial amino acids present at the catalytic active site and peripheral anionic site of AChE. Compound 3h would be a promising drug candidate to treat AD as a selective and dual binding site inhibitor of AChE.