Copper(II) complexes of methimazole, an anti Grave’s disease drug. Synthesis, characterization and its potential biological behavior as alkaline phosphatase inhibitor

Potential bio-protective effect of copper compounds: mimicking SOD and peroxidases enzymes and inhibiting acid phosphatase as a target for anti-osteoporotic chemotherapeutics

Copper complexes with transformed methimazole ligand have been synthesized and characterized by elemental analysis, conductivity measurements, thermogravimetric analysis, EPR, FTIR and UV-Vis spectroscopies. Results support their stoichiometries and geometrical structures: [Cu(C₄H₅N₂S)₂Cl₂]·2H₂O(1), [Cu(C₈H₁₀N₄S)SO₄H₂O](2) and [Cu(C₈H₁₀N₄S)SO₄](3). ((C₄H₅N₂)₂S: bis(l-methylimidazol-2-yl)sulfide; (C₄H₅N₂S)₂ = Bis[bis(l-methylimidazol-2-yl)disulfide]) Concurrently, the structurally distinct soluble species corresponding to complexes (1) and (2) were subsequently used in an in vitro investigation of their potential biological properties. In view of their possible pharmaceutical activity, the complexes were in vitro evaluated as phosphatase acid inhibitors. Their radical bio-protective effects were also studied measuring the effect against DPPH^• and O₂^•- radicals. Additional catalytic properties as peroxidase mimics were evaluated using Michaelis-Menten kinetic model by means of phenol red and pyrogallol assays. The complexes exhibited catalytic bromination activity and the ability to oxidize pyrogallol substrate indicating that they can be considered as functional models. The relationships between the structures and the in vitro biological activities have also been considered. Serum protein albumin has attracted the greatest interest as drug carrier and the affinity of biological/pharmaceutical compound is relevant to the development of new medicine. In that sense, interaction studies by fluorescence and EPR spectroscopies were performed showing the binding capacity of the complexes.

Zinc(II)-methimazole complexes: synthesis and reactivity

The tetrahedral S-coordinated complex [Zn(MeImHS)4](ClO4)2, synthesised from the reaction of [Zn(ClO4)2] with methimazole (1-methyl-3H-imidazole-2-thione, MeImHS), reacts with triethylamine to yield the homoleptic complex [Zn(MeImS)2] (MeImS = anion methimazole). ESI-MS and MAS (13)C-NMR experiments supported MeImS acting as a (N,S)-chelating ligand. The DFT-optimised structure of [Zn(MeImS)2] is also reported and the main bond lengths compared to those of related Zn-methimazole complexes. The complex [Zn(MeImS)2] reacts under mild conditions with methyl iodide and separates the novel complex [Zn(MeImSMe)2I2] (MeImSMe = S-methylmethimazole). X-ray diffraction analysis of the complex shows a ZnI2N2 core, with the methyl thioethers uncoordinated to zinc. Conversely, the reaction of [Zn(MeImS)2] with hydroiodic acid led to the formation of the complex [Zn(MeImHS)2I2] having a ZnI2S2 core with the neutral methimazole units S-coordinating the metal centre. The Zn-coordinated methimazole can markedly modify the coordination environment when changing from its thione to thionate form and vice versa. The study of the interaction of the drug methimazole with the complex [Zn(MeIm)4](2+) (MeIm = 1-methylimidazole) - as a model for Zn-enzymes containing a N4 donor set from histidine residues - shows that methimazole displaces only one of the coordinated MeIm molecules; the formation constant of the mixed complex [Zn(MeIm)3(MeImHS)](2+) was determined.

Copper as a key regulator of cell signalling pathways

Copper is an essential element in many biological processes. The critical functions associated with copper have resulted from evolutionary harnessing of its potent redox activity. This same property also places copper in a unique role as a key modulator of cell signal transduction pathways. These pathways are the complex sequence of molecular interactions that drive all cellular mechanisms and are often associated with the interplay of key enzymes including kinases and phosphatases but also including intracellular changes in pools of smaller molecules. A growing body of evidence is beginning to delineate the how, when and where of copper-mediated control over cell signal transduction. This has been driven by research demonstrating critical changes to copper homeostasis in many disorders including cancer and neurodegeneration and therapeutic potential through control of disease-associated cell signalling changes by modulation of copper-protein interactions. This timely review brings together for the first time the diverse actions of copper as a key regulator of cell signalling pathways and discusses the potential strategies for controlling disease-associated signalling processes using copper modulators. It is hoped that this review will provide a valuable insight into copper as a key signal regulator and stimulate further research to promote our understanding of copper in disease and therapy.