The oxidation of aminoethylcysteine ketimine dimer by oxygen reactive species

The prominent spontaneous reaction of aminoethylcysteine ketimine in the neutral pH range is the concentration-dependent dimerization (Hermann, 1961). The carboxylated dimer first produced loses the free carboxyl yielding the more stable decarboxylated dimer (named simply the dimer in this note). In the search for a possible biochemical activity of this uncommon tricyclic compound we have assayed whether it could interact with oxygen reactive species (H2O2, O2 (-),(•)OH) thus exhibiting a scavenging effect of possible biomedical interest. The dimer interacts with H2O2 producing compounds detectable by chromatographic procedures. The presence of Fe(2+) stimulates the oxidative reaction by yielding the hydroxyl radical (the Fenton reaction). Using the system xanthine oxidase-xanthine as superoxide producer, the dimer oxidation by O2 (-) has also been documented. Among the oxidation products the presence of taurine and cysteic acid has been established. Identification of remaining oxidation products and investigation of the possible function of the dimer as a biological scavenger of oxygen reactive species are now oncoming.