Non-enzymic browning: the reaction between d-glucose and glycine in the ‘dry’ state

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Abstract
The reaction between D-glucose and glycine in the "dry" state at 37[degree], pH 6.7 and 70% relative humidity was studied chromatographically and spectroscopically. An intermediate appeared which gave the color reactions of both a sugar and an amino acid. The intermediate was isolated pure from the reaction mixture by displacement chromatography on an ion-exchange resin. It is very strongly reducing but is not a ketose. Glucosazone can be formed from it. On oxidation with sodium metaperiodate it released 3 molecular proportions of formic acid and also formaldehyde. On treatment with acid it gave 5-hydroxymethylfurfuraldehyde and glycine. The infrared spectrum of the Na salt of the intermediate is consistent with that expected for the Na salt of the enolic form of N-(carboxymethyl) amino-1-deoxy-fructose. On this evidence the intermediate was formulated as the enolic form of N-(carboxymethyl)-amino-l-deoxyfructose, with the tautomeric equilibrium completely in favor of the enol. The compound was a true intermediate in the "Browning" reaction.