Evaluation of Antioxidant Activity of Functionalizated Vinylic Tellurides

The aim of the present study was to evaluate antioxidant properties of (Z) 1- (4-mehtylphenylsulfonyl)-2- (phenyltelluryl)-2- phenylethene (compound 1a), (Z) 1- (thiophenyl)-2-(buthyltelluryl)-2-phenylethene (compound 1b), (Z) 1- (thiomethyl)-2- (buthyltelluryl)-2-phenylethene (compound 1c) and (Z) 1- (thiobenzyl)-2-(butyltelluryl)-heptene (compound 1d). Mice were decapitated and liver tissue was rapidly homogenized yielding a low-speed supernatant fraction (S₁). The level of lipid peroxides in the reaction was measured by the method of Ohkawa et al. (1979) using MDA (malondialdehyde) as an external standard. An aliquot of S₁ was added to the reaction mixture containing: 100 mM FeSO₄, 50 mM EDTA and compounds at different concentrations (1- 200 mM).  FeSO₄ and EDTA were used as classical inductors of lipid peroxidation. The reactive species (RS) measurement were determined by a spectrofluorimetric method, using 2’,7’- dichlorofluorescein diacetate (DCHF-DA) assay. The oxidation of DCHF-DA to fluorescent dichlorofluorescein (DCF) is measured for the detection of intracellular RS.  The DCF fluorescence intensity emission was recorded at 520nm (with 480 nm excitation) 15 min after the addition of DCHF-DA to the medium. Data were analyzed statistically by one-way ANOVA, followed by Duncan’s Multiple Range Test when appropriate. Compounds 1b, 1c and 1d at 1 mM were effective in reducing lipid peroxidation induced in liver of mice. However, compound 1a was only effective in reducing lipid peroxidation induced at 10 mM. Compound 1c presented lesser IC₅₀ against lipid peroxidation than other compounds (1c≥1d>1b>1a). The maximal inhibitory effect was in the following order 1a=1b=1c=1d. In fact, these compounds protected against lipid peroxidation about 75 %. Furthermore, compound 1a demonstrated IC₅₀ of 293.90 mM and the maximal decrease of reactive species in the fluorimetric assay was 60%. Conversely, compounds 1b, 1c and 1d presented poor antioxidant profiles (IC₅₀ > 400 mM) when compared to 1a in the fluorimetric assay.  In conclusion, considering the potent in vitro antioxidant activity of these compounds, more detailed pharmacological studies involving organotellurium compounds are need.