Extract of and Its Components Interacting with Sulfide, Cysteine and Glutathione Increase Their Antioxidant Potencies and Inhibit Polysulfide-Induced Cleavage of Plasmid DNA.

Aqueous root extract from (ASRE) has a wide range of medicinal effects. The present work was aimed at studying the influence of sulfide, cysteine and glutathione on the antioxidant properties of ASRE and some of its selected phytochemical components. Reduction of the 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazol-1-yloxy-3-oxide (cPTIO) stable radical and plasmid DNA (pDNA) cleavage in vitro assays were used to evaluate antioxidant and DNA-damaging properties of ASRE and its individual components. We found that the interaction of ASRE and its two components, caffeic acid and chlorogenic acid (but not protocatechuic acid and eleutheroside B or E), with HS/HS, cysteine or glutathione significantly increased the reduction of the cPTIO radical. In contrast, the potency of ASRE and its selected components was not affected by NaS, oxidized glutathione, cystine or methionine, indicating that the thiol group is a prerequisite for the promotion of the antioxidant effects. ASRE interacting with HS/HS or cysteine displayed a bell-shaped effect in the pDNA cleavage assay. However, ASRE and its components inhibited pDNA cleavage induced by polysulfides. In conclusion, we suggest that cysteine, glutathione and HS/HS increase antioxidant properties of ASRE and that changes of their concentrations and the thiol/disulfide ratio can influence the resulting biological effects of ASRE.