Estudos eletroquímicos de derivados 5-nitrotiofeno-tiossemicarbazônicos: compostos de interesse biológicos

Abstract

Due to their known biological properties, aromatic nitrocomposites are widely applied in the pharmaceutical industry, mainly because of their likely mechanisms of action to occur through oxirreduction reactions. The identification of nitro and its products by a simple, sensitive and low cost technique as the electrochemical techniques is fundamental, because through them it is possible to analyze the solubilization process of these compounds in association with some encapsulating agents. The present work aimed at electrochemical studies of 5-nitrotiophene-thiosemicarbazonic derivatives, compounds of proven biological activities. UV-Vis spectroscopic studies were performed in aqueous-ethanolic medium at different times. The electrochemical system used was composed of 3 electrodes, Ag / AgCl / Cl-saturated (reference), platinum wire (auxiliary), glassy carbon and gold (Au) (working), in pH 7.0 buffered medium. For the stability study, 2- (5-nitro-thiophene) thiosemicarbazonic derivatives did not suffer degradation under the conditions analyzed. The 5-nitrotiophene-thiosemicarbazonium derivatives have standard reduction mechanism of potential nitroaromatics within the expected range for compounds with biological activity, where substitutions did not compromise the base mechanism, presenting small potential changes. β-Cyclodextrin was tested as an encapsulating agent and demonstrated efficiency for complex formation with the test compound, with LNN5 presenting the best electrochemical profile and by forming a self-organized β-CD-SH monolayer (SAM). Au electrode, it was possible to determine the apparent association constant between the LNN5: β-CD complex with a value of 2.78 x 104 M-1 and obtained LD and LQ values were 0.20 and 0.68 μmol L-1. respectively. As for the interaction of compounds with DNA, LNN1, LNN5 and LNN6 derivatives react with ssDNA in solution reducing their analytical signal and interact with dsDNA mainly in guanine nucleobases. In the presence of oxygen, LNN5 and LNN6 presented an interaction with oxygen.