IR, NMR, XPS study of 1-(d-3-mercapto-2-methylpropionyl)-l-proline and its zinc complexes

Synthesis and characterization of a cobalt(III) complex with 1-(D-3-mercapto-2-methylpropionyl)-L-proline

The reaction of CoCl2 with 1-(D-3-mercapto-2-methylpropionyl)-L-proline (L or captopril) yields a new nanocrystalline complex with general formula [CoL2(OH)]2. The complex has been characterised with infrared (IR) and ultra-violet visible (UV-vis) spectroscopies, magnetic measurements, X-ray photoelectron spectroscopy (XPS), and wide angle X-ray scattering (WAXS). XPS analyses is a valuable tool for studying the chemical composition and the chemical state of elements at the surface of solids whereas WAXS provides information on the short range order. A model is proposed for the binding of the complex and its structure: the Co(III) ion is bonded with a pseudo-octahedral configuration. Captopril molecules are coordinated via mercapto group and amidic C=O group to Co(III) ions: two S atoms are bridging bonded between two Co(III) ions. The OH- ion completes the coordination around the Co(III).

Free radical scavenging and copper chelation: a potentially beneficial action of captopril

Captopril (CpSH), an angiotensin converting enzyme (ACE) inhibitor, is reported to provide protection against free-radical mediated damage. The purpose of this study was to investigate, by means of pulse radiolysis technique, the behaviour of CpSH towards radiation-induced radicals in the absence and in the presence of copper(II) ions, which can play a relevant role in the metal catalysed generation of reactive oxygen species. The results indicate that the -SH group is crucial in determining the radical scavenging action of CpSH and the nature of the resulting CpSH transient products in the absence or in the presence of oxygen. In the presence of Cu(II), the -SH group is still involved in the biological action of the molecule participating both in the one-electron reduction of Cu(II) with formation of CpSSCp, and in Cu(I) chelation. This conclusion is supported by the Raman spectroscopic data which allow to identify the CpSH sites involved in the copper complex at different pH. These results suggest that CpSH may potentially inhibit oxidative damage both through free radical scavenging and metal chelation. Considering the low CpSH concentration in vivo, the metal chelation mechanism, more than the direct radical scavenging, could play the major role in moderating the toxicological effects of free radicals.

X-ray photoelectron spectra of complexes with 1-(D-3-mercapto-2-methylpropionyl)-L-proline and Ni(II), Cd(II) and Cu(I): synthesis and LAXS study of Cu(I) derivative

Metal complexes of general formula Na2M(CAP)2xH2O (with M = Cd(II) or Ni(II), x = 7 and 4, respectively, CAP = 1-(D-3-mercapto-2-methylpropionyl)-L-proline) and NaCuCAPx3H2O have been synthesized as amorphous compounds and studied by means of X-ray photoelectron spectroscopy (XPS). Cu(I) derivative has been studied by IR, XPS and large-angle X-ray scattering (LAXS). IR data and the chemical shift of core level signals suggest that CAP is bonded to the metal via the sulphur atom and the carbonylic oxygen. LAXS data confirm this finding and are consistent with a tetrahedral configuration around the copper ion. The CAP molecule is bonded through the sulphur and the carbonylic oxygen and two water molecules complete the coordination around the metal. The sodium ion exhibits a tetrahedral configuration and interacts with the carboxylic group and two water molecules. One of these is bridging bonded between copper and sodium. No metal-nitrogen bonds are present.