aldose

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.

Objective: To develop a rapid and sensitive sugar detection method for research and commercial use, as well as to understand the sugar composition in dietary beverages and functional foods.

Results: Five beverages in Taiwan were examined for the composition of six common sugars. Two Solanaceae samples extracted from the potato and tomato plants were measured by MALDI MS and ESI-MS/MS. The structures of solanines were elucidated and the glycan moieties were converted to the fluorescent NAIM derivatives to confirm their composition.

Conclusions: The results suggest that the aldo-NAIM method is efficient and rapid for evaluation of sugar composition and concentration in beverages and foods.