Structural elucidation of the oxidation product of aminoethylcysteine ketimine decarboxylated dimer by peroxynitrite

Conversion of the mycotoxin patulin to the less toxic desoxypatulinic acid by the biocontrol yeast Rhodosporidium kratochvilovae strain LS11

The infection of stored apples by the fungus Penicillium expansum causes the contamination of fruits and fruit-derived products with the mycotoxin patulin, which is a major issue in food safety. Fungal attack can be prevented by beneficial microorganisms, so-called biocontrol agents. Previous time-course thin layer chromatography analyses showed that the aerobic incubation of patulin with the biocontrol yeast Rhodosporidium kratochvilovae strain LS11 leads to the disappearance of the mycotoxin spot and the parallel emergence of two new spots, one of which disappears over time. In this work, we analyzed the biodegradation of patulin effected by LS11 through HPLC. The more stable of the two compounds was purified and characterized by nuclear magnetic resonance as desoxypatulinic acid, whose formation was also quantitated in patulin degradation experiments. After R. kratochvilovae LS11 had been incubated in the presence of (13)C-labeled patulin, label was traced to desoxypatulinic acid, thus proving that this compound derives from the metabolization of patulin by the yeast. Desoxypatulinic acid was much less toxic than patulin to human lymphocytes and, in contrast to patulin, did not react in vitro with the thiol-bearing tripeptide glutathione. The lower toxicity of desoxypatulinic acid is proposed to be a consequence of the hydrolysis of the lactone ring and the loss of functional groups that react with thiol groups. The formation of desoxypatulinic acid from patulin represents a novel biodegradation pathway that is also a detoxification process.

Antioxidant properties of aminoethylcysteine ketimine decarboxylated dimer: a review

Aminoethylcysteine ketimine decarboxylated dimer is a natural sulfur-containing compound detected in human plasma and urine, in mammalian brain and in many common edible vegetables. Over the past decade many studies have been undertaken to identify its metabolic role. Attention has been focused on its antioxidant properties and on its reactivity against oxygen and nitrogen reactive species. These properties have been studied in different model systems starting from plasma lipoproteins to specific cellular lines. All these studies report that aminoethylcysteine ketimine decarboxylated dimer is able to interact both with reactive oxygen and nitrogen species (hydrogen peroxide, superoxide anion, hydroxyl radical, peroxynitrite and its derivatives). Its antioxidant activity is similar to that of Vitamin E while higher than other hydrophilic antioxidants, such as trolox and N-acetylcysteine.

Measurement of sulfur-containing compounds involved in the metabolism and transport of cysteamine and cystamine. Regional differences in cerebral metabolism

An HPLC method with coulometric detection is presented for the quantitation of cysteamine, cystamine, thialysine, glutathione, glutathione disulfide and an oxidized metabolite of thialysine [S-(2-aminoethyl)-L-cysteine ketimine decarboxylated dimer (AECK-DD)]. The advantage of coulometric detection is that derivatization is unnecessary if the analyte is redox sensitive. The method was used to quantitate several sulfur-containing compounds in plasma and brain following gavage feeding of cysteamine to rats. Cysteamine, cystamine, thialysine and AECK-DD were detected in the brains of these animals. Interestingly, cysteamine treatment resulted in greatly elevated levels of cerebral methionine, despite the fact that cysteamine is not a precursor of methionine.

Synthesis and characterization of a dehydrogenation product arising from the oxidation of aminoethylcysteine ketimine decarboxylated dimer

While investigating the antioxidant properties of aminoethylcysteine ketimine decarboxylated dimer (1) (a natural substance occurring in biological fluids such as human urine and plasma and in bovine cerebellum), a previously unreported oxidation product was obtained. This compound was identified and characterized through comparison with an authentic sample prepared via Pd-catalyzed dehydrogenation of 1. This molecule is an example of an alternative oxidation pathway involving 1.