New Colored Compounds from the Maillard Reaction between Xylose and Lysine

An aqueous xylose−lysine model system was heated for 1 h under reflux, and the colored ethyl acetate-extractable compounds were separated. The structural elucidation of the first three-ring colored compound ever isolated from this Maillard model system and the partial characterization of a second one are described. Structure elucidation was based mostly on heteronuclear two-dimensional NMR. Keywords: Maillard reaction; nonenzymic browning; colored compounds; lysine; xylose; heteronuclear two-dimensional NMR