Chemical characterization of fucoidans isolated from Laminaria angustata var. Longissima

Abstract

We isolated and characterized several fucoidans from a kind of brown seaweeds, Laminaria angustata var. longissima., which has been eaten for about 300 years in Okinawa, Japan. The polysaccharides were extracted with 0.1 mol/L HCl, and partially purified with cetylpyridinium chloride. The partially purified polysaccharides were fractionated by anion exchange chromatography, and four fractions (LA-1, LA-2, LA3 and LA-4) were obtained. There was difference in the ratio of chemical composition of LA-1, LA-2, LA-3 and LA-4, but each fraction contained L-fucose residues and sulfate groups. Molecular weight of LA-1, LA-2, LA3 and LA-4 were 27.7×104, 1.0×10 4, 0.8×104 and 1.9×104, respectively. The 1H-NMR spectroscopy analysis of LA-2, which was the main fraction, and the desulfated LA-2 suggested that LA-2 consisted of the main chain of (1→-3)-linked α-L-fucopyranosyl residues, a part of which had (1→2)-linked-α-L-fucopyranosyl residues at the C2 position, and these residues had sulfate group at the C4 position. It was suggested that the fractions LA-3 and LA-4 were the mixture of fucoidan and galactan sulfate.