FORMATION OF PROLINE-SPECIFIC AND HYDROXYPROLINE-SPECIFIC MAILLARD PRODUCTS FROM [1-13C]GLUCOSE

The Maillard reactions of [1-C-13]glucose with proline and hydroxyproline, respectively, were investigated to gain more insight into the reaction pathways involved. Among others, maltoxazine, cyclotene, cyclopenta[b]azepinones and pyridinones, 2-acetyltetrahydropyridine, dihydropyrrolizines, and several hydroxyproline-derived pyrrolyl and tetrahydroindolizinone compounds were analyzed by capillary GC/MS, and the extent and position of isotopic labeling were determined by interpretation of the MS data. The results were used to evaluate the so fu postulated routes to these compounds. Caused by the observed distribution of the isotopic label, the structure of one of the products was reinvestigated and identified as 5-acetyl-7-methyl-1,2,3,4-tetrahydrofuro[3,4-b]pyridine (15), the first derivative of this type of bicyclic heterocycle isolated in Maillard model reactions.