Methylglyoxal, degradation

Figure 7 Mechanism of gloxylase I in methylglyoxal degradation. See text for details...

Methylglyoxal (MG) and Insulin Resistance MG Formation and Degradation MG Formation... 

In the sample based on MIL and methylglyoxal, the ratio of Strccker aldehyde to sotolone was about 1 2 at pH 5 (Table VT). Consequently, the Slrecker degradation of HIL is a competitive reaction to the formation of sotolone. In contrast. only traces of Strecker aldehyde were detected In the sample containing the laciom-ADF, i.e about 50 times less than in the reaction with HIL 1 he formation orsololoiir from ADF is the favoured reaction, most likely due to the blocked carboxyl pmnp... 

Schulz et al. [234] used dehydro-Shinoda-ascorbic acid, which is the first characteristic intermediate of L-ascorbic acid degradation via the oxidative route, as a starting material of the reaction to distinguish it from the nonoxidative pathway. They found that dehydro-L-ascorbic acid yielded five a-dicarbonyl compounds, namely glyoxal, methylglyoxal, diacetyl, L-threosone, and 3-deoxy-L-threosone (Figure 11.16). They concluded that these a-dicarbonyl compounds are formed from L-ascorbic acid on the oxidative pathway. But, they pointed out that these products can also be produced via the nonoxidative route. They also found that 3-deoxy-L-pentosone is exclusively formed via the nonoxidative route. 

Figure 4.60 Degradation of methylglyoxal and hydroxyacetone. Other reactions of fragments...

Thiazole itself is smelling like pyridine, but substituted thiazoles, such as 2-acetylthiazole and 2,4-dimethyl-5-vinylthiazole, generally have a desirable odour, frequently described as nutty, green, roasted and vegetable-like. For example, the Strecker degradation of cysteine by methylglyoxal yields 2-acetylthiazole in thermally processed foods (Figure 8.83). A possible intermediate of this reaction is 2-acetyl-2-thiazoline with an intense aroma of fresh bread crust, which is similar to the odour of 2-acetyl-... 

By retro-aldol cleavages of the 1-deoxyosone short-chain dicarbonyls like diacetyl, methylglyoxal or hydroxydiacetyl are formed which - like the deoxyosones - may participate in the Strecker degradation of amino acids, thus creating volatile flavor components 17,18). On the other hand, the 1-deoxyosone undeigoes several cyclization reactions yielding e.g. acetylfiiran, maltol, isomaltol, furaneol and 5-hydroxy-5,6-dihydromaltol (DHM) (75). 

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