Oxygen-Dependent Fragmentation Reactions during the Degradation of 1-Deoxy-d-erythro-hexo-2,3-diulose

Abstract

With this work, we report on further insights into the chemistry of 1-deoxy-D-erythro-hexo-2,3-diulose (1-deoxyglucosone, 1-DG). This alpha-dicarbonyl plays an important role as a highly reactive intermediate in the Maillard chemistry of hexoses. Degradation of 1-DG in the presence of the amino acid l-alanine led to the formation of several products. Lactic acid and glyceric acid were found to be major degradation products. Their formation was dependent on the presence of oxygen. Therefore, a mechanism is postulated based on oxidation leading to a tricarbonyl intermediate. Carbonyl cleavage of this structure should then give rise to carboxylic acids. This mechanism was supported by the isotope distribution observed during degradation of different (13)C-labeled D-glucose isotopomers. Furthermore, we identified 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (gamma-pyranone) to be capable of rehydration forming 1-DG to a minor extent and therefore leading to the same degradation products. The formation of carboxylic acids from gamma-pyranone was also dependent on the presence of oxygen in agreement with the postulated oxidative fragmentation. Finally, we investigated the formation of aldehydes expected as retro-aldol products formed within the degradation of 1-DG. Results seemed to rule out this reaction as an important degradation pathway under the conditions investigated herein.

Pathways of the Maillard reaction under physiological conditions

“…Again, Davidek et al were the first to perform detailed mechanistic studies [72,73]. The results were confirmed by investigations of our workgroup [74,75]. We studied the degradation of 1-DG which is isomerized into its 2,4-tautomer.…”

Changes in Maillard reaction products in ghee during storage

“…It has been proposed that water addition to pyranone ( Fig. 1) regenerates the highly reactive 1-deoxyglucosone (Kim & Baltes, 1996;Voigt et al, 2010). The reactive 1-deoxyglucosone, depending on the conditions, can then form numerous compounds including acetic acid (Voigt & Glomb, 2009;Voigt et al, 2010).…”

“…For example, pyranone (Kim & Baltes, 1996), acetylformoin (Hofmann, 1998), and 1-deoxyglucosone (Davidek, Robert, Devaud, Vera, & Blank, 2006;Voigt & Glomb, 2009;Voigt et al, 2010) have all been shown to produce the same numerous end products of glucose degradation. Furthermore, pyranone and DHHD formed compounds (e.g., acetic acid, formic acid, lactones) that are best explained by conversion to deoxyglucosone followed by hydrolytic and oxidative fragmentation.…”

“…1) to produce 5 and 6-membered ring compounds, such as acetylformoin (right branch of Fig. 1) and 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (pyranone), respectively (Kim & Baltes, 1996;Voigt & Glomb, 2009;Voigt, Smuda, Pfahler, & Glomb, 2010). Acetylformoin is notable in that it has a linear tautomer (3,4-dihydroxy-3-hexen-2,5-dione, DHHD, Fig.…”

“…Possible reaction pathways for the reactive glucose derivative, 1-deoxyglucosone (taken fromHodge et al, 1972;Voigt et al, 2010).…”