Chemistry and Biological Effects of Melanoidins and Glyceraldehyde-Derived Pyridinium as Advanced Glycation End Products

Abstract

Abstract: Blue pigments (blue-M1 and blue-M2) and red pigments (red-M1 and red-M2) were generated in a xylose-glycine reaction system. Blue-M2 was identified as an addition compound of di-xylulose-glycine to blue-M1 that involved two pyrrolopyrrole structures. We identified red pigments as isomers of addition compounds of xylulose-glycine to the condensed compound between pyrrolopyrrole-2-carbaldehyde and pyrrole-2-carbaldehyde. These pigments have polymerizing activity, suggesting that they are important Maillard reaction intermediates through the formation of melanoidins. Melanoidins induced IFN-γ and IL-12 expression in spleen cells exposed to allergen and in macrophages, respectively. These findings suggest that melanoidins have a suppressive effect on allergic reaction as a novel physiological effect. On the other hand, we identified a glyceraldehyde-derived advanced glycation end product (AGE) formed from glyceraldehyde and N-acetylarginine as well as glyceraldehyde-derived pyridinium (GLAP) in physiological conditions. The AGE was identified as 5-methylimidazoline-4-one (MG-H1), which has been reported to be formed from arginine and methylglyoxal. GLAP, which induced reactive oxygen species (ROS) production in HL-60 cells, is supposed to be a toxic AGE, while MG-H1 is a nontoxic AGE.