Amadori derivatives

The Amadori derivative of lysine and glucose (c-deoxyfruc-tosyllysine) is not biologically available to rats (9,28). The same has been observed also with the other Amadori compounds of lysine (a- and a-c-di-derivatives) and those Amadori compounds derived from other amino acids such as methionine (29), tryptophan (12,30,32), and leucine (12). 

Under the conditions corresponding to the roasting of coffee, serine, threonine, and sucrose yield various substituted pyridines (51), furans, and furanones (52). Thirty-three pyridine derivatives were identified by Baltes and co-workers (51), Recently, 3-methylthiomethylpyridine was identified as one of the products of thermal degradation of the glucose-methionine Amadori intermediates (53). 

Hashiba, H. The browning reaction of Amadori compounds derived from various sugars. Agric. Biol. Chem. 1982, 47, 547-8. 

Takeoka et al. (5) also reported methods for derivatizing both aliphatic and aromatic Amadori compounds as -nitrobenzyloxy-amine (PNBO) derivatives to allow facile UV detection in the pico-molar range for HPLC separations. They reported in the same paper a simple method for derivatizing the Amadori compounds to allow gas chromatographic/mass spectrometric (GC/MS) separation and identification of highly purified Amadori compounds. 

Only recently have N -nitroso Amadori compounds been characterized chemically. The first description of an -nltroso derivative of an Amadori compound reported the formation of 1-deoxy-l-(N -nitroso-3,4-xylidino)-D-f ructose to confirm that a secondary amino group had been formed in an Amadori compound ( 6). Coughlin et al. ( 7) and Heyns et al. ( 8) described the formation of nitrosated Amadori compounds. Since Amadori compounds are weakly basic secondary amines and occur widely in Maillard browned foods and beverages ( 5) and unburned tobacco ( ), the genotoxic potential of these compounds is of interest. 

Figure 2. Helicoidal structure of Amadori-lype sugar derivatives of poly-L-lysine.

Coleman, W. M., and Chung, H. L. (2002). Pyrolysis GC-MS analysis of Amadori compounds derived from selected amino acids and glucose. /. Anal. Appl. Pyrolysis 62, 215-223. 

Another possible mechanism7 for the transformation of sugars with amino acids into colored products is through the Amadori rearrangement,44 which is the isomerization of an aldosylamine to a ketose derivative, for example, of a D-glucosylamine derivative to a derivative of 1-amino-l-deoxy-D-fruc-tose. Such a conversion has been shown to occur when an amino acid reacts... 

Results of the many investigations into the mechanism of the Maillard reaction support one of two main theories. The first assumes the formation of glycosylamines which undergo the Amadori (or, for ketoses, the Heyns) rearrangement. The 1-amino-1-deoxyketose derivative (or 2-amino-2-de-... 

The furan isomaltol (7) and the pyran maltol ( 8 ) (Scheme 3) are consistent with having been formed via a 1-deoxyosone intermediate. Cyclization of such an intermediate and the loss of 2 additional moles of water allow one to arrive at these structures. Data which supports this is found in papers by Hodge and his group (1 3), who synthesized 1-deoxy-l-piperidino-maltulose (J5, Scheme 4) and showed that on further heating, it was converted to galactosyl isomaltol (JJJ). This is convincing evidence that isomaltol is sugar derived and is produced from an Amadori compound. Furthermore, the structure is wholly consistent with the formation of a 4-0-substituted 1-deoxyosone as an intermediate in the reaction. 

The finding that the furanone is produced from an Amadori compound was interesting in that it permitted us to test, for the first time, the effect of pH on the products of the reaction. This is not possible using a hexose- derived Amadori compound, because the end products are not stable. The product of 1,2-enolization (3-deoxyosone intermediate) is HMF, which is stable, but the product derived from 2,3 enolization (1-deoxyosone intermediate), maltol and isomaltol are not stable in aqueous solution and thus cannot be detected and measured accurately. In our experiment (Scheme 6), we prepared 1-deoxy-dibenzylamino (13), and -benzylamino (12) D-fructuronic acids, as well as... 

Although some investigators believe that dihydrofuranone is derived from ribose-5-phosphate through a dephosphorylation-dehydration mechanism, others believe it can be formed by a typical Halliard reaction betveen amines and sugars, in which the Amadori products dehydrate and eliminate to amines. Both routes are likely to occur. 

Furfural identified in beef diffusate appears to be a prominent meat flavor intermediate. It is a dehydration product of pentoses similar to formation of hydroxy methyl furfural from hex-oses. These compounds are formed by dehydration of 1,2-enediols derived from deamination of Amadori compounds (51). 

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