Structural characterization of an anticoagulant-active sulfated polysaccharide isolated from green alga Monostroma latissimum

The green alga Monostroma latissimum was boiled in hot water to obtain an anticoagulant-active polysaccharide. The crude polysaccharide was further purified on ion-exchange and size-exclusion chromatography to generate a polysaccharide PML of uniform size and charge. PML was a high rhamnose-containing sulfated polysaccharide with an average molecular weight of about 513 kDa. On the basis of detailed one- and two-dimensional nuclear magnetic resonance (1D, 2D NMR) spectroscopic analyses, the chain of the polysaccharide was characterized to consist of (1 → 3)-linked α-l-rhamnopyranose, (1 → 2)-linked α-l-rhamnopyranose and (1 → 2,3)-linked α-l-rhamnopyranose residues in a molar ratio of 4:1:1, and the sulfate groups were substituted at C-2 of the (1 → 3)-linked α-l-rhamnopyranose and C-3 of the (1 → 2)-linked α-l-rhamnopyranose residues. PML had a high anticoagulant activity as evaluated by assays of the activated partial thromboplastin time and thrombin time. The investigation demonstrated that PML appeared to be a sulfated rhamnan with different structural characteristics from other sulfated polysaccharides from Monostromaceae species, and could be a potential source of anticoagulant.