A new method for aldo-sugar analysis in beverages and dietary foods

摘要

Background: Carbohydrates are found in most of our everyday diet; however, sugar analysis is difficult and inconvenient in food materials such as beverages, fruits and vegetables. Here, we report a new method for labeling the sugar ingredients in beverages and plant foods. The mentioned method provides a high sensitive and efficient tool for sugar compositional analysis by labeling the aldoses in beverages and foods with 2,3-naphthalenediamine via an iodine-promoted oxidative condensation reaction to form highly fluorescent aldo-naphthylimidazole (NAIM) derivatives. We have also separated the natural glycosides from dietary foods, for instance, solanines from tomato and potato. The various types of solanines with different sugar moieties were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). The glycan is released by acidic hydrolysis, and the sugar components are subjected to NAIM labeling. These aldo-NAIM derivatives not only show enhanced mass signaling, but also provide fluorescent moiety at the reducing end of sugar to assist the detection in HPLC analysis.