A disaccharide repeat unit is the major structure in fucoidans from two species of brown algae

The predominant repeating structure of a fraction of the fucoidan from Asco phyllum nodosum prepared by acid hydrolysis and centrifugal partition chrom atography (LMWF) was established as: [ --> 3)-alpha -L-Fuc(2SO(3)(-))-(1 --> 4)-alpha -L-Fuc(2,3diSO(3)(-))-(1]( n) by NMR spectroscopy and methylation analysis. The proton and carbon NMR spe ctra of this unit have been assigned and found to correspond with features in the spectra of the whole purified fucan from A. nodosum which account fo r most of the integrated intensity. The same structure has also been recogn ised in the fucoidan of Fucus vesiculosus. The fraction LMWF has in vitro a nticoagulant activity, indicating that the above structure may be partly re sponsible for biological activity in the native fucoidan. (C) 2001 Elsevier Science Ltd. All rights reserved.