Estudos bioeletroquímicos de derivados do 5-nitrotiofeno-tiossemicarbazônico visando entendimento de sua ação biológica e aumento de solubilidade

Abstract

The planning and development of new therapeutic agents, nitroheterocyclic compounds are of great importance, enabling the introduction of various substituent radicals, which gives the compounds different activities and properties, both chemical and biological. Its bioreduction mechanism can be reproduced in electroanalytical cells and identified via electrochemical methods. A characteristic common to many nitrocomposites (such as those under study) is the low solubility in water, which justifies its association with versatile substances such as cyclodextrin, which can form inclusion complexes with a variety of molecules. In the present study, an amino β-cyclodextrin graft was performed on glassy carbon electrodes, through the amine electrooxidation, without the need for additional ligands or intermediates; then, the formation of inclusion complexes between 5-nitrothiophene-thiosemibazonic derivatives (LNN) and β-cyclodextrin (β-CD) was evaluated using Differential Pulse Voltammetry (VPD). The electrochemical system was composed of 3 electrodes, Ag / AgCl / Cl-saturated (reference), platinum (auxiliary), glassy carbon (CV) with immobilized β-cyclodextrin amino (work), in buffered medium pH 7.00 with ethanol as co-solvent. UV-Vis studies were also carried out in an aqueous medium containing 5% –ethanol, varying the concentration of β-Cyclodextrin. The CV-amino-β-cyclodextrin platform made it possible to analyze the interaction of 5-nitrothiophene-thiosemibazonic derivatives with β-CD, which was identified by linearly increasing the peak current of the analyte as a function of the increase in the concentration of the same until the saturation point between the substances Through the β-CD immobilized on the electrode surface, it was possible to calculate the equilibrium constant between the studied derivatives and the cyclodextrin with values of 5.87x104 L mol-1 for LNN01, 2.199x105 L mol-1 for LNN03, 7.61x105 L mol-1 for LNN05 and 2.33x103 L mol-1 for the LNN06. Also calculated by spectrophotometric methods, the average constants were 2.107x105 L mol-1 for LNN01, 2.174x106 L mol-1 for LNN03 and 2.223x105 L mol-1 for LNN05. Both constants demonstrate good formation of the complexes between the LNN: β-CD. Cyclodextrin is already considered a pharmaceutical excipient, used in drugs, so its good results via electrochemistry with the studied derivatives are quite hopeful in a future association and development of a drug.