fucoidan, a complex sulfated containing substantial percentages of l-fucose and sulfate ester groups, is a constituent of brown algae and some marine invertebrates. besides l-fucose, it frequently contains d- xylose, d-galactose, d-mannose and d -glucuronic acid. fucoidan has no determined molecular formula, and its structure built up mainly of (1 ?/span> 2)-linked, 4- o -sulfated fucopyranose residues has been generally accepted for fucoidan from l.aminaria japonical / undaria pinnatifida.