Non-enzymatic glycation of melamine with sugars and sugar like compounds

Melamine (1,3,5-triazine-2,4,6-triamine) is employed in the manufacture of plastics, laminates and glues, yet, it has been found sometimes added illegally to dairy products to artificially inflate foods’ protein content. In 2008, dairy products adulterated with melamine were blamed for the death of several infants in China, a situation that forced Beijing to introduce stricter food safety measures. The objectives of this study were threefold: (1) to investigate the susceptibility of the amine groups of melamine to glycation with d-galactose, d-glucose and lactose, sugars commonly found in milk, (2) to study the rate and extent of melamine’s glycation with methylglyoxal, glyoxal and DL-glyceraldehyde, three highly reactive metabolites of d-galactose, d-glucose and lactose, and (3) to characterize, using mass spectrometry, the Advanced Glycation Endproducts (AGEs) of melamine with sugars found commonly in milk and their metabolites. Incubation of d-galactose, d-glucose and lactose with melamine revealed that d-galactose was the most potent glycator of melamine, followed by d-glucose, then lactose. Methylglyoxal, glyoxal, and DL-glyceraldehyde glycated melamine more extensively than d-galactose, with each yielding a broader range of AGEs. The non-enzymatic modification of melamine by sugars and sugar-like compounds warrants further investigation, as this process may influence melamine’s toxicity in vivo.

The glycation of melamine with glyoxal, DL-glyceraldehyde and d-galactose as elucidated by mass spectrometry was postulated to proceed via the Amadori pathway in a manner similar to that of methylglyoxal.Figure optionsDownload as PowerPoint slideHighlights
► We demonstrated for the first time the non-enzymatic glycation of melamine.
► The formation of melamine’s glycation products occurred via Amadori pathway.
► Of sugars found in milk, d-galactose was the most potent glycator of melamine.
► Of milk sugar metabolites, glyoxal was the most potent glycator of melamine.
► The extent of melamine’s glycation was dependent on temperature and pH.