Structure of a fucoidan from the brown seaweed Fucus serratus L.

A fucoidan consisting Of L-fucose, sulfate and acetate in a molar proportion of 1:1:0.1 and small amounts of xylose and galactose were isolated from the brown seaweed Fucus serratus L. The fucoidan structure was investigated by 1D and 2D H-1 and C-13 NMR spectroscopy of its desulfated and de-O-acetylated derivatives as well as by methylation analysis of the native and desulfated polysaccharides. A branched structure was suggested for the fucoidan with a backbone of alternating 3- and 4-linked alpha-L-fucopyranose residues, 3)-alpha-L-Fucp-(1 -> 4)-alpha-L-Fucp-(1 -> about half of the 3-linked residues being substituted at C-4 by trifucoside units alpha-L-Fucp-(1 -> 4)-alpha-L-Fucp-(1 -> 3)-alpha-L-Fucp-(1 ->. Minor chains built up of 4-linked alpha-fucopyranose and beta-xylose residues were also detected, but their location, as well as the position of galactose residues, remained unknown. Sulfate groups were shown to occupy mainly C-2 and sometimes C-4, although 3,4-diglycosylated and some terminal fucose residues may be nonsulfated. Acetate was found to occupy C-4 of 3-linked Fuc and C-3 of 4-linked Fuc in a ratio of about 7:3. (c) 2005 Elsevier Ltd. All rights reserved.