A study of fucoidan from the brown seaweed Chorda filum

Fucoidan fractions from the brown seaweed Chorda filum were studied using s olvolytic desulfation. Methylation analysis and NMR spectroscopy were appli ed for native and desulfated polysaccharides. Homofucan sulfate from C. fil um was shown to contain poly-alpha-(1-->3)-fucopyranoside backbone with a h igh degree of branching, mainly of alpha-(1-->2)-linked single units. Some fucopyranose residues are sulfated at O-4 (mainly) and O-2 positions. Some alpha-(1-->3)-linked fucose residues were shown by NMR to be 2-O-acetylated . The H-1 and C-13 NMR spectra of desulfated, deacetylated fucan were compl etely assigned. The spectral data obtained correspond to a quasiregular pol ysaccharide structure with a branched hexasaccharide repeating unit. Other fucoidan fractions from C. filum have more complex carbohydrate composition and give rather complex methylation patterns. [GRAPHICS] (C) 1999 Elsevier Science Ltd. All rights reserved.