Brown seaweed contains several
polysaccharides like
laminaran,
fucoidan and
alginate.
Laminaran is a
beta-glucan that has shown anti-apoptotic and anti-tumoral activities, while
galactofucan (
fucoidan) is a sulfated
polysaccharide that has displayed
anticoagulant, anti-
tumor, anti-
thrombosis, anti-inflammatory and
antiviral properties. In this study, crude
laminaran and
galactofucan (
fucoidan) were extracted from the brown seaweed Saccharina longicruris at four harvest periods (M05, A05, N05 and J06). The
galactofucan M05 and N05 fractions were depolymerized (RDP) over 2 or 4h to give 4 RDP fractions (M05 RDP 2H, M05 RDP 4H, N05 RDP 2H and N05 RDP 4H) whose molecular weights,
monosaccharide compositions and glycosidic linkages were determined by GC-MS. The
laminaran fraction gave a molecular weight range from 2900 to 3300 Da and contained between 50.6% and 68.6%
d-glucose and an average of 1.3%
D-mannitol. The presence of a beta-(1,3) linkage between
D-glucose in the main chain was observed, with branching at positions 6 and 2. The M05 fraction contained less branching than other
laminaran fractions, which might have influenced its conformation in
solution and thus its activity. The crude
galactofucan fractions displayed a molecular weight range from 638 to 1529 kDa, whereas the RDP fractions had molecular weights <30 kDa. The structure of the
galactofucan fractions remained complex after depolymerization, with these also being more sulfated (30-39%) than the crude fractions (13-20%). The crude and RDP fractions contained 3-linked fucopyranose 4-sulfate and 6-linked
galactopyranose 3-sulfate moieties, although the galactofucans isolated from M05 and J06 contained less 6-linked
galactopyranose 3-sulfate than the A05 and N05 fractions.