GAS-CHROMATOGRAPHIC DETERMINATION OF N-CARBOXYMETHYL AMINO-ACIDS, THE PERIODATE-OXIDATION PRODUCTS OF AMADORI COMPOUNDS

Periodate oxidation of Amadori compounds (1-amino-1-deoxy-2-ketoses), formed by the glycoslyation of primary amino groups of free amino acids or N-terminal and epsilon-lysyl amino groups in peptides and proteins with aldoses, leads to the formation of N-carboxymethyl amino acids. The latter are then analysed by gas chromatography as their ethyl ester N-ethoxycarbonyl derivatives, after a straightforward derivatization reaction with ethyl chloroformate in a mixture of ethanol, pyridine and water. The amounts of N-carboxymethylated amino acids directly reflect the extent of glycosylation of the various amino sites. Application of this approach to food products is discussed.