Selective detection of lactolated peptides in hydrolysates by liquid chromatography/electrospray tandem mass spectrometry

In food processing as well as in human nutrition and physiology, the increasing importance of the Maillard reaction has brought about the need for analytical means to detect and characterize the protein-bound Amadori products. In this paper, we describe a highly selective and sensitive method for detecting peptides glycated with lactose (lactolated peptides) from a complex hydrolysate using electrospray ionization tandem mass spectrometry. Protonated molecular ions of lactolated peptides gave a product-ion spectrum, with the dominant mode of decomposition including cleavage of the O-glycosidic bond followed by dehydration steps giving a characteristic neutral loss of 216 Da. Optimization of the ion marker [M + H]+− 216, identified as a furylium ion, was investigated. It remained dominant regardless of the nature of the glycated peptides, the collision energy used, or the charge state of the parent ion. An approach for detecting lactolated peptides from protein digest was proposed during reverse-phase high-performance liquid chromatography (HPLC)/electrospray mass spectrometry and reverse-phase HPLC/tandem mass spectrometry using neutral loss scanning. This technique detected picomole amounts of lactolated peptides.