Determination of hydroxytryptophan isomers in gamma-irradiated egg white, chicken meat, and shrimps

The radiation induced products of tryptophan (TRP) were determined in gamma-irradiated egg white, chicken meat and shrimps using RP-HPLC and electrochemical detection. A two-step hydrolysis with proteinase K and carboxypeptidase A was developed to release the radiation products from egg white and chicken meat and with proteinase K and pronase E from shrimps. The four hydroxytryptophan isomers (OH-Trp) were identified and quantified as radiation products in all samples. The amounts ranged between 0.02 and 1.97 mg/kg protein. A significant difference between irradiated and unirradiated samples was found for irradiation doses of more than 3 kGy for egg white and chicken meat. For shrimps no significant increase of OH-Trp isomers was measured up to a radiation dose of 5 kGy.

Contaminants in biotechnologically manufactured L-tryptophan

The epidemic outbreak of a new disease, the eosinophilia-myalgia syndrome (EMS), was traced back to the intake of L-tryptophan (Trp) of certain lots from a single manufacturer. Since some trace contaminants were related to EMS, it appeared to be necessary to identify and find the origin of most trace contaminants in the EMS related Trp in order to apply this knowledge to a prospective manufacturing practice. Seventeen contaminants were determined in an implicated Trp lot by a single reversed-phase high-performance liquid chromatography run using UV and fluorescence detection. Most of these contaminants were classified as Trp metabolites, non-physiological oxidation or carbonyl condensation compounds of Trp. The amount and the pattern of contaminants were compared with recently manufactured Trp and Trp-containing preparations.

Formation of N-formylkynurenine suggests the involvement of apolipoprotein B-100 centered tryptophan radicals in the initiation of LDL lipid peroxidation

Tryptophan oxidation products were determined in pronase E digests of apo B of delipidated, native and Cu2+ oxidized LDL using a sensitive and specific HPLC method. Oxidized LDL contained N-formylkynurenine, kynurenine and tryptamine but no oxindolylalanine and 5-hydroxytryptophan. N-Formylkynurenine increased from an initial value of 0.21 to 1.67 mol/mol apo B within 5 h. Apo B of native LDL also contained kynurenine (0.80 mol/mol) and tryptamine (0.13 mol/ mol). The results support the assumption that oxidation of Trp residues in apo B is an early event and possibly an elementary reaction involved in initiating LDL oxidation.