Novo Synthesis of Amino Acids during the Maillard Reaction: qTOF/ESI Mass Spectrometric Evidence for the Mechanism of Akabori Transformation

The transformation of α-amino acids into their hydroxymethyl derivatives during the Maillard reaction is an intriguing possibility for catalysis by metal salts in the presence of Strecker aldehydes; the process is commonly known as the Akabori reaction. The mechanism of this reaction was studied in the presence of glucose, using glycine copper complex and paraformaldehyde as Akabori model system in aqueous mixtures heated at 110 °C for 2 h and subsequently analyzed by qTOF/ESI/MS. Isotope-labeling studies of the various products identified have provided for the first time mass spectrometric evidence for the detailed mechanism of Akabori transformation, particularly the formation of Schiff base adducts prior to the final conversion into serine and hydroxymethyl-serine. Furthermore, the results have indicated that sugars do not interfere with such transformations and, on the contrary, the presence of glycine–copper complexes in the Maillard model systems can enhance the production of Maillard reaction intermediates.