56821-76-2Relevant academic research and scientific papers
Reactivity of Selenocystine and Tellurocystine: Structure and Antioxidant Activity of the Derivatives
Satheeshkumar, Kandhan,Raju, Saravanan,Singh, Harkesh B.,Butcher, Ray J.
supporting information, p. 17513 - 17522 (2018/11/23)
l-Selenocystine (5) and l-tellurocystine (6) have been prepared and the reactivity of these amino acids, i.e., oxidation of 5 and 6, has been performed at various pH values. Hydrogen peroxide was used as an oxidant and it was treated with 5 and 6 in excess in acidic and basic media. Compound 5, upon oxidation, afforded SeIV and SeVI products. Selenocysteic acid [HO3SeCH2CH(NH2)COOH] 9, a novel SeVI compound, was isolated and characterised by single-crystal X-ray diffraction studies. In contrast, l-tellurocystine, upon oxidation with H2O2, afforded TeII and TeIV products. Zwitterionic organotellurolate(IV), [TeCl3CH2CH(NH3)COOH] 13, was isolated and characterised by NMR and IR spectroscopy, mass spectrometry and elemental analysis. Compound 13 crystallizes in an orthorhombic space group. l-Tellurocystine, when reduced with NaBH4, produced the desired tellurolate intermediate, which was trapped with bromoacetic acid. Furthermore, l- and d-tellurocysteine derivatives, [(RTeCH2CH(NH2)COOH) R=phenyl, substituted phenyl and naphthyl (24–39)] were synthesised and evaluated for their glutathione peroxidase (GPx)-like activities. The results show that l-tellurocysteine derivatives have higher activity than their D-tellurocysteine analogues. DFT calculations for l-tellurocysteine derivatives provided information about the bond lengths and bond angles. This study reveals that the introduction of naphthyl substituents (35–38) leads to twisted conformation of the amino acid derivatives.
Thiol peroxidase activity of diaryl ditellurides as determined by a 1H NMR method
Engman, Lars,Stern, David,Cotgreave, Ian A.,Andersson, Carl M.
, p. 9737 - 9743 (2007/10/02)
A 1H NMR method was developed for the assessment of the glutathione peroxidase-like activity of synthetic compounds. In this assay, thiols (N-acetylcysteine, tert-butyl mercaptan and 1-octyl mercaptan) were oxidized to the corresponding disulfides in CD3OD or CD3OD/D2O in the presence of hydrogen peroxide and the catalyst to be evaluated. The time required to reduce the thiol concentration with 50%, t50, was determined as a measure of the thiol peroxidase activity of the catalyst. Several diaryl ditellurides were efficient catalysts when present in low concentrations (0.3 mol %), whereas compounds with well-documented glutathione peroxidase-like activity in other assays were inactive (Ebselen, diaryl diselenides). The glutathione peroxidase-like activity of diaryl ditellurides was also assessed by using the classical coupled reductase assay. A mechanistic study showed that diaryl ditellurides, in the presence of hydrogen peroxide and a thiol, were rapidly converted to tellurosulfides. These species were stable enough to be isolated in some cases. The tellurosulfides reacted very slowly with added thiol, but in the presence of thiol/hydrogen peroxide the thiol was rapidly converted to its corresponding disulfide. On the basis of these observations, a mechanism involving a tellurinic acid thiol ester was proposed for the thiol peroxidase reaction of ditellurides. In contrast to tellurosulfides, selenosulfides, obtained either from diphenyl diselenide/hydrogen peroxide/1-octyl mercaptan or from Ebselen and 1-octyl mercaptan, were found to react very slowly with thiols in the presence of hydrogen peroxide.
