Characterization of laminaran and a highly sulfated polysaccharide from Sargassum fusiforme

•Three polysaccharides HFS-1, HFS-2, and HFS-3 were isolated from S. fusiforme.•HFS-1 was composed of soluble laminaran with chains that are terminated by β-d-glucose residues.•HFS-2 was a mixture of alginate and sulfated heteropolysaccharide.•HFS-3 has a sequence of 3-linked fucopyranose interspersed by galactopyranose or galactooligosaccharides.

The crude polysaccharide (HFS) from Sargassum fusiforme (Hizikia fusiforme) was extracted using 0.1 M HCl and was fractionated by anion-exchange chromatography into three fractions: HFS-1, HFS-2, and HFS-3. Based on the chemical analysis, HFS-1 was composed of laminaran, HFS-2 was a mixture of alginate and sulfated heteropolysaccharides, and HFS-3 was primarily composed of sulfated galactofucan. The NMR spectra revealed that HFS-1 was composed of a soluble laminaran with chains that are terminated by β-d-glucose residues. In contrast, the spectra obtained for HFS-2 were still complex, even after most of the alginate was removed. In addition, HFS-3 might contain 3-linked fucan sulfated at C-2, 6-linked galactan sulfated at C-2 and branched at C-4 by 2-sulfated Fuc, and galactofucan with a backbone of either alternating Gal and Fuc sulfated at C-2 or alternating (Gal)n and (Fuc)n sulfated at C-2. Moreover, HFS-3 also contained small amounts of fucoglucuronomannan and xylan.

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