Síntese e caracterização estrutural de complexos envolvendo os fármacos maleato de enalapril, hidroclorotiazida e clortalidona

Abstract

The research of drugs mechanism of action has been held continuously in order to elucidate the molecular structure and functional groups of interest. It is important for the suitable pharmacological activity. Since the mechanism of action of the enalapril maleate antihypertensive drug is related to the formation of a in vivo complex with the Zn2+ present in the active site of carboxypeptidase enzyme (ECA), this work consisted of synthesis and structural characterization of five metal complexes of Zn2+ with the enalapril maleate, hydrochlorothiazide and chlorthalidone drugs, in addition to obtaining a new derivate of the chlorthalidone drug. The most used technique for structural characterization is the X-ray diffraction, thus this work describes the characterization using this technique applied to single crystals, in three novel compounds. In addition to X-ray diffraction, other techniques such as vibrational spectroscopy in the infrared and Raman, thermogravimetric analysis, elementar analysis of carbon, hydrogen, nitrogen and chlorine (CHNCl) were used. Among the complexes formed, only those that contain the drug enalapril were characterized by X-ray diffraction. In the formation of complexes involving the enalapril drug, was noted that the synthesis by slowing addition gives rise to a metal complex in which only the maleate ion is present in the structure. In order to obtain a complex in which the drug active principle, the enalapril, was present, was proposed a new synthetic route. In this synthesis the first step was the removal of the maleate ion of the solution, followed by addition of the Zn2+ metal ion. The new complex formed showed the enalapril drug coordinated to the zinc by oxygen atom of the carboxylate group in monodentate mode. Thus the metal ion has a tetrahedral geometry indicating that in vitro the enalapril complexation with the Zn2+ ion is similar to what is suggested in vivo. This complex crystallizes in C222 space group and is stabilized by hydrogen bonds. The structure crystal obtained also revealed the presence occupational disorder in the oxygen atom of the perchlorate counter ion. In order to alleviate this disorder, it made a new measure of this single crystal at low temperature. At the end of this measure was perceived the occurrence of an order-disorder phase transition, since the crystal structure of the complex enalapril-Zn (ENAZn) is ordened at low temperature and disordened at room temperature. These complexes are conformational polymorphs presenting the main difference in their structures the torsion angles. From the spectroscopic analysis could be inferred that the hydrochlorothiazide and chlorthalidone drugs coordinated Zn2+ ion in a chelate mode by

γ-lactam group and the heterocyclic ring, respectively. In addition a new derivative of the chlorthalidone drug was obtained using a synthesis with a stove for heating. A mechanism for the formation of this new derivate of chlorthalidone was proposed in which the Zn(ClO4)2 acts a Lewis acid. This compound was characterized by X-ray diffraction and showed orthorhombic crystal system with Pca21 space group. Were also to obtained single crystals of pure hydrochlorothiazide and chlorthalidone drugs that were also analyzed by X-ray diffraction.