Copper (II) complexes derived from pyridoxal: Structural correlations, cytotoxic activities, and molecular docking

Abstract

This article presents the synthesis, characterization, evaluation of the mimetic potential of the catalytic activity of the superoxide dismutase enzyme, cytotoxic effects, evaluation of interactions with CT-DNA, and theoretical calculations of copper (II) mononuclear complexes. The C1, C2, and C3 complexes were obtained from the aldolic condensation between aromatic amines (furfurylamine, 2-thiophenethylamine, and 2-thiophenethylamine) and aromatic aldehydes (salicylic aldehyde, ortho-vanillin, and pyridoxal hydrochloride). The compounds were structurally characterized by X-ray diffraction, cyclic voltammetry, FTIR, and ultraviolet/visible spectroscopies. Although the complexes presented coordination modes with identical organic molecules, there were different coordination geometries. In addition, the varied chalcogen substituents revealed an electrochemical potential quite different from the complexes. The synthesized complexes were subjected to NBT photoreduction (nitrotetrazolium blue chloride) to quantify the antioxidant activity, and values of the McCord-Fridovich assay showed that the synthesized complexes have significant superoxide dismutation activity. Moreover, CuII complexes were tested in fluorimetric assays, colorimetric assays to assess cellular metabolic activity, and the dichlorofluorescein diacetate test. Our findings showed that the C2 complex presented the best antioxidant activity with the safest reactive oxygen species generation levels and the least damage to DNA using the evaluated methods. Finally, we evaluated how the synthesized complexes interacted with calf thymus deoxyribonucleic acid by spectroscopic techniques (absorption and emission) and theoretical calculations.