Heat deterioration of phospholipids. V. A new rearrangement reaction of sugars and phosphatidylethanolamine.

Novel four 2,3-dihydro-1H-imidazo[1,2-a]pyridine-4-ylium derivatives were obtained with increase of UV absorption at 350 nm and browning of the solution by heating paste lecithin from soybean (SL) in octane. These four derivatives were formed by reaction of one molar of any sugar except 2-deoxysugars with two molar of phosphatidylethanolamines (PE) in SL. To confirm the reaction mechanism, several (13)C-labeled-sugars were reacted with 1,2-di-O-stearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE), respectively. These reactants clearly showed that five carbons of the pyridinium ring and one carbon of the substituted group were based on those of a sugar and that the formation of the pyridinium derivatives was accompanied with cleaving between the carbons of 1- and 2-positions in the sugar and rearrangement. This reaction is a new rearrangement reaction and we named it "new pseudo Maillard rearrangement reaction".