Isolation and partial characterization of a novel β-d-galactan sulfate from the brown seaweed Laminaria angustata var. longissima

Abstract

The fastest-moving component (LA-5) on electrophoresis was isolated from a sulfated polysaccharide fraction of the brown seaweed Laminaria angustata var. longissima by anion-exchange chromatography, fractional precipitation with ethanol, and gel filtration. LA-5 consisted of galactose, fucose, glucuronic acid and sulfate (100:2:3:74) and had an apparent average molecular weight of 400 000. The results of enzymatic digestion, optical rotation and 13C-NMR suggested that galactose is present predominantly as the beta-D-form in LA-5. By IR, 13C-NMR and methylation analyses, LA-5 has been shown to have a backbone of leads to 3)-beta-D-galactosyl-(1 leads to 6)-beta-D-galactosyl-(1 leads to. Most sulfate groups may be attached to position 6 of 3-linked galactosyl residues. This indicates that the polysaccharide is a new type of galactan sulfate different from the well known galactans from red seaweeds and ascidians. This is the first report on the presence of galactan sulfate in the brown seaweeds.