Synthesis, characterization and distinct butyrylcholinesterase activities of transition metal complexes of 2-[(E)-(quinolin-3-ylimino)methyl]phenol

2-[(E)-(Quinolin-3-ylimino)methyl]phenol (H-QMP) was synthesized by condensing salicylaldehyde with 2-aminoquinoline and fully characterized by mass spectrometry, 1H and 13C{1H}NMR, and IR spectroscopies. The metal complexes [M(QMP)(OAc)]H2O where M = Cu(II) and Zn(II) and [M(QMP)2] where M = Ni and Co(II) were prepared from the metal acetates. All transition metal complexes were assigned geometries based on the UV–Vis spectra, conductivity and magnetic susceptibilities. [M(QMP)2], {where M = Ni and Co(II)}, were further characterized by single crystal X-ray diffraction and were found to be pseudo-octahedral with interquinoline interaction to the metal center. The complexes were screened for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Only cobalt and copper containing complexes were found to be active against BChE with IC50 = 69 ± 0.0112 and 5 ± 0.0004 μM ± SEM, respectively. Surprisingly no activity was observed for AChE, therefore selective BChE inhibition was observed for copper and cobalt complexes only.

Graphical abstractTransition metal complexes of new quinolone based Schiff base ligands were synthesized and characterized. These complexes were screened for their AChE and BChE inhibition activities.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis of Schiff base ligand and its complexation with Co, Ni, Cu and Zn(II) metals. ► Spectroscopic characterization of ligand and complexes. ► Single crystal structural analysis of cobalt and nickel complexes. ► Acetylcholinesterase and butyrylcholinesterase inhibition activities of all the synthesized compounds.