Abstract: Sea cucumber chondroitin sulfate (CHS) is one of the important bioactive substancesins in sea cucumber body wall. Since its multiple bioactive functions have been validated, CHS is considered as a potential ingredient of novel functional foods. Similar to most carbohydrates, CHS lacks specific chromophores and fluorescence groups. Based on this background, the aim of this study was to construct fluorescence labelling of CHS. The polysaccharide was derivatized by hydrogen bromide activation method with 6-amino-fluorescein as the fluorescent dye. As a result, each molecule of the labelled product approximately contained 4.4 molecules of 6-amino-fluorescein. The optimal fluorescence excitation and emission wavelengths of the labelled CHS were 495 and 520 nm, respectively. Additionally, its molecular weight and sulfate content were determined. Infrared spectroscopy showed that the structural characteristics of the polysaccharide did not significantly change after labeling. The labelled CHS exhibited strong fluorescence intensity and stability in neutral and alkaline environments. The influence of NaCl in the solution environment on the labelled CHS was limited. The establishment of this fluorescence labeling method will facilitate further research on the absorption and metabolism, functions and underlying mechanisms of CHS and its interactions with other biomolecules.

Key words: sea cucumber chondroitin sulfates, fluorescence labeling, 6-aminofluorescein, stability, sea cucumber