Identification of new heterocyclic nitrogen compounds from glucose-lysine and xylose-lysine maillard model systems

Aqueous sugar (glucose or xylose)-lysine model systems were heated at 80 de greesC for 6 h with the pH maintained at a predetermined value (3, 4, or 5) . Selected compounds were isolated by combinations of solvent extraction an d semipreparative HPLC, prior to identification by NMR and mass spectrometr y. Two compounds were identified from the pH 5 glucose system and were iden tified as epsilon-[2-formyl-5-(hydroxymethyl)pyrrole-1-yl]-L-norleucine (py rraline) and the new compound, 1-(5-carboxy-5-aminopentyl)-2-formyl-3-(1,2, 3 -trihydroxypropyl)pyrrole. A third compound was partially characterized. 2-Acetyl-5-hydroxymethyl-5,6-dihydro-4H-pyridinone was identified in the pH 3 xylose system, and the new compound, 8-furan-2-yl-methyl-5-hydroxymethyl -5,6 dione, was identified in the pH 4 xylose system. 2-Furfurylidene-4-hyd roxy-5-methyl-3(2H) was identified in both xylose systems. Mechanisms of fo rmation are proposed for the novel compounds.