Convenient synthesis of lactuloselysine and its use for LC-MS analysis in milk-like model systems.

The synthesis of the Amadori product lactuloselysine [N-(1-deoxy-D-lactulosyl-1)-L-lysine] was obtained starting from FMOC-lysine-OH (NR-9-fluorenylmethoxy-carbonyl-NH2-L-lysine-OH) and lactose. Compound identity was confirmed by MALDI-ToF, electrospray, and NMR analysis. A selective LC-MS procedure which allowed the detection of lactuloselysine up to 10 ng mL-1 was set up and used to follow the formation of the compound in a lactose-lysine model system; quantification of this molecule after complete enzymatic hydrolysis of whey-proteins from milk samples was also performed.