Formation of the N,N′-Dialkylpyrazine Cation Radical from Glyoxal Dialkylimine Produced on Reaction of a Sugar with an Amine or Amino Acid

Abstract

The formation of an intermediate product, which could easily give a radical product, in an early stage of the Maillard reaction was confirmed commonly occur in various sugar-amino compound systems, by detection of the N,N′-dialkylpyrazine cation radical generated on the addition of ascorbic acid (AsA) to the reaction mixtures. This intermediate was produced immediately after to glycosylamine formation, prior to Amadori rearrangement, and completely parallel to the formation of glyoxal dialkylimine, which was identified by TLC as a main component of the extract. Authentic glyoxal dialkylimine was shown to produce an identical radical on treatment with both reducing agents and acids instead of AsA. It was thus demonstrated that the intermediate is glyoxaldialkylimine and that acid hydrolysis followed by reduction is required for production of the free radical.