Chemical Characterization of Fucoidans Isolated from Laminaria angustata var. Longissima

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, LA-3 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, LA-3 and LA-4 were 27.7 X 10(4), 1.0 x 10(4), 0.8 X 10(4) and 1.9 X 10(4), respectively. The H-1-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 alpha-L-fucopyranosyl residues, a part of which had (1 -> 2)-linked-alpha-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. (Received Mar. 23, 2010; Accepted Aug. 2, 2010)