Carbohydrate and Amino Acid Degradation Pathways in l-Methionine/d-[13C] Glucose Model Systems

Maillard model systems consisting of labeled d-[13C]glucoses, l-[15N]methionine, and l-[methyl-13C]methionine, have been utilized to identify the amino acid and carbohydrate fragmentation pathways occurring in the model system through Py-GC/MS analysis. The label incorporation analyses have indicated that the carbohydrate moiety produces 1-deoxy- and 3-deoxyglucosones and undergoes C2/C4 and C3/C3 cleavages to produce glycolaldehyde, tetrose, and C3-reactive sugar derivatives such as acetol, glyceraldehyde, and pyruvaldehyde. Glycolaldehyde was found to incorporate C-1, C-2 (70%) and C-5, C-6 (30%) glucose carbon fragments, whereas the tetrose moiety incorporates only C-3, C-4, C-5, C-6 glucose carbon atoms. In addition, the major source of reactive C3 fragments was found to contain C-4, C-5, C-6 sugar moiety. On the other hand, methionine alone also generated Strecker aldehyde as detected by its condensation product with 3-(methylthio)propylamine. Plausible mechanisms were proposed for the formation of t...