A fluorometric assay for quantification of fucoidan, a sulfated polysaccharide from brown algae

Brown algae contain a fucose- rich sulfated polysaccharide called fucoidan which is a constituent of the extracellular matrix. In recent years, fucoidan has attracted much attention for its pharmaceutically important biological activities. To develop a superior method for fucoidan quantification, we investigated several cationic dyes with potential interaction with the negatively charged sulfate groups of fucoidan and found that a commercially available fluorescent dye, SYBR Gold nucleic acid gel stain, showed a clear fluorescence enhancement upon mixing with authentic fucoidan. A standard curve generated with the dye and authentic fucoidan showed a linear dynamic range of 0.05- 2.5 ng mu l(-1), and the limits of detection and quantification of fucoidan were 0.025 and 0.075 ng mu l(-1), respectively. Neither nucleic acids nor alginates, anionic polymers present in brown algae, interfered with the quantification of fucoidan, which is simply extracted with diluted HCl from sporophytes of the brown alga Saccharina japonica. The fluorometric microplate method in this study is simple, sensitive, and widely applicable to fucoidan quantification.