Antinociceptive property of vinyl sulfides in spite of their weak antioxidant activity

Vinyl sulfides (a–c), a new class of organosulfur compounds, were screened for antioxidant and antinociceptive activities. In view of this, in vitro antioxidant effect was investigated through the determination of the thiobarbituric acid reactive substances and protein carbonyl levels in rat brain homogenate. Considering the results obtained in vitro, antinociceptive activity of vinyl sulfides (a–c) (5–50 mg/kg, intragastrically) was investigated in a model of nociception induced by glutamate (20 μmol/paw, 20 μl, intraplantar) in mice. A close inspection of the results revealed that unsymmetrical substituted vinyl sulfides (compounds a–c) presented weak antioxidant activity against lipid peroxidation and protein carbonilation in vitro. In vivo experiments showed that compounds a, b, and c, at all doses (5–50 mg/kg), caused an inhibition of the licking and edema induced by glutamate in mice. However, antinociceptive action of sulfides was not dose-dependent, as well as the antioxidant effect was not concentration-dependent. Thus, chemical structure of vinyl sulfides is not related with pharmacological effects. The results demonstrated that vinyl sulfides presented weak antioxidant effect and potent antinociceptive and antiedematogenic effect.