Synthesis, structural characterization and cholinesterase and ?-glycosidase inhibition of heterometallic Co-Ni/Zn/Fe maleate complexes

Abstract

Heterometallic coordination compounds based on biologically relevant metal ions have attracted considerable attention due to their structural diversity and potential biological activity. In this work, new heterometallic maleate complexes were synthesized and investigated. Novel heterometallic maleate complexes of nickel(II), zinc (II), and iron(II) were obtained by the interaction of bis(hydrogen maleate)cobalt(II) tetrahydrate with Ni(II), Zn (II), and Fe(II) acetates and nitrates. It was found that depending on the nature of the metal ion, the concentration of the reagents, and the counter-anion, polymeric heterometallic maleate complexes are formed along with monomeric heterometallic maleate complexes of the composition [CoM(mal)2(H2O)4] (M = Ni, Zn, Fe). The composition and structure of the obtained complexes were studied by IR, UV-Vis, EPR spectroscopy, cyclic voltammetry, and thermogravimetric analysis. Molecular and crystal structures of the monomeric maleates Zn-Co, Ni-Co, and Fe-Co were determined by single-crystal X-ray diffraction (SCXRD). The activities of Ni, Mn, and Co metal complexes against various proteins, namely acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and alpha-glycosidase (alpha-Gly), were compared. Heterometallic Ni-Co (4Ni) and Zn-Co (5Co) maleate complexes, as well as the Mn complex (2Mn) used for comparison, were evaluated for their inhibitory activities against acetylcholinesterase, butyrylcholinesterase, and alpha-glycosidase. The 2Mn complex exhibited the most potent AChE inhibition with an IC50 value of 0.67 & micro;M and a K; value of 1.03 & micro;M, significantly outperforming the reference inhibitor tacrine. Notably, the 5Co complex showed strong alpha-glycosidase inhibition (IC50 =1.01 & micro;M, K; = 2.37 & micro;M), exceeding the activity of acarbose. These results demonstrate that heterometallic maleate complexes exhibit pronounced and selective multi-enzyme inhibitory activities depending on the metal ion composition. The study highlights the influence of the metal center on both the structural features and the biological activity of the complexes. These findings suggest that heterometallic maleate complexes may represent promising candidates for further investigation as enzyme inhibitors.