Electrochemical behavior and anti/prooxidant activity of thioethers with redox-active catechol moiety

A number of asymmetrical thioethers combining sterically hindered catechol moiety and different groups (polar, non-polar, or redox active) at sulfur atom have been synthesized. Redox transformations of sulfides were studied by cyclic voltammetry. The electrooxidation of thioethers at the first stage leads to the formation of o-benzoquinones. The presence of a redox-active thioether linker and additional phenolic fragment favors to an extension of the range of redox properties for such functionalized catechols. The introduction of the thioether fragment into catechol ring affects not only the electrochemical behavior of the compounds, but also the antioxidant activity. The antioxidant activities of the compounds were evaluated using 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH) assay, the oxidative damage of the DNA, the reaction of 2,2′-azobis(2-amidinopropane dihydrochloride) (AAPH)-induced glutathione depletion, and the process of lipid peroxidation of rat liver (Wistar) homogenates in vitro. The compounds have greater antiradical effect than 3,5-di-tert-butylcatechol (CatH2) in DPPH assay. In the course of the AAPH-induced oxidative DNA damage, all tested compounds exhibit inhibitory activity unlike CatH2. Among the compounds under investigation, three catechol thioethers reveal mostly antioxidant properties. Several compounds with polar groups possess dual anti/prooxidant activity. The thiolation of catechol ring can change properties of target thiothers by a variation of different organic fragments at sulfur atom.