Extract from Conyza canadensis as a modulator of plasma protein oxidation induced by peroxynitrite in vitro

The antioxidative activity of the extract from Conyza canadensis in plasma treated with peroxynitrite (ONOO-) (0.1 mM) was studied. C. canadensis is known to possess a broad set of pharmacological effects because of content of various antioxidants, antiplatelet and anticoagulant compounds. The aim of our study was to assess if this extract protects plasma proteins against oxidative/nitrative damages induced by ONOO-. The plasma components are continuously exposed to reactive oxygen/nitrogen species action. Peroxynitrite evokes oxidative stress and induces undesirable effects in biological systems and causes damage to biomolecules. The extract from Conyza (50-2500 mg/ml) caused a dose-dependent reduction of protein nitration by 90%. The oxidation of plasma proteins was diminished by about 75%. ONOO- oxidized the plasma thiol groups and this process was inhibited by tested extract. The level of reduced protein thiols was increased thrice at the lowest concentration of extract (50 mg/ml). The highest concentration of extract decreased twice the level of protein thiols in reduced forms and increased the homocysteine level about 4.5 times. The obtained results demonstrated that the extract from Conyza possesses antioxidative properties in vitro, protects plasma proteins against toxicity induced by peroxynitrite and has modulating effects on thiol/disulfide redox status.