title: Thiol-induced hydroxyl radical formation and scavenger effect of thiocarbamides on hydroxyl radicals.
abstract: The effects of thiols and thiocarbamides on hydroxyl radical (.OH) formation by the hypoxanthine(HYP)-xanthine oxidase(XOD)-Fe3+ .EDTA system were investigated in the range of 0.5-5 mM by colorimetrically measuring salicylate hydroxylation. Thiocarbamides powerfully inhibited the hydroxylation while thiols showed a paradoxical effect, enhancing it at low concentrations, but inhibiting it at high ones. Thiols in the presence of Fe3+ .EDTA generated superoxide anions (O2-.) and .OH during the oxidation, but thiocarbamides did not. A study of the effect of ergothioneine, a thiocarbamide present in mammals, on the .OH spin adduct of 5,5-dimethyl-1-pyrroline-N-oxide(DMPO) by EPR spectrometry showed that it effectively decreased the .OH spin adduct without causing the appearance of other signals. Reaction mechanisms are proposed for the O2-. evolution and .OH formation by the thiols themselves in the presence of Fe3+ .EDTA and .OH with thiols and thiocarbamides.
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003124:Colorimetry; D004492:Edetic Acid; D005609:Free Radicals; D006900:Hydroxylation; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000032:analysis*; D013481:Superoxides; D013859:Thiocarbamates / Q000032:analysis*; D014969:Xanthine Oxidase / Q000378:metabolism
chemical_list: D005609:Free Radicals; D013438:Sulfhydryl Compounds; D013859:Thiocarbamates; D013481:Superoxides; D004492:Edetic Acid; D014969:Xanthine Oxidase