A rhamnan-type sulfated polysaccharide with novel structure from Monostroma angicava Kjellm (Chlorophyta) and its bioactivity

A homogeneous polysaccharide was obtained from Monostroma angicava Kjellm by water extraction, preparative anion-exchange and size-exclusion chromatography. Results of chemical and spectroscopic analyses showed that the polysaccharide was a glucuronic acid-containing rhamnan-type sulfated polysaccharide. The backbone mainly consisted of →3)-α-l-Rhap-(1→ and →2)-α-l-Rhap-(1→ residues, partially sulfated at C-2 of →3)-α-l-Rhap-(1→ and C-3/C-4 of →2)-α-l-Rhap-(1→. The branching contained unsulfated or monosulfated 3-linked, 2-linked, 4-linked α-l-rhamnose and terminal β-d-glucuronic acid residues. The polysaccharide had strong antidiabetic activity assessed by glucose consumption, total cholesterol and triglyceride levels using human hepatocellular carcinoma (HepG2) and insulin-resistant HepG2 cells. The polysaccharide exhibited high anticoagulant property by activated partial thromboplastin time and thrombin time assays, and possessed high fibrin(ogen)olytic activity evaluated by plasminogen activator inhibitior-1, fibrin(ogen) degradation products and D-dimer levels using rats plasma. The investigation demonstrated that the polysaccharide from Monostroma angicava Kjellm was a novel sulfated rhamnan and could be a potential antidiabetic and anticoagulant polysaccharide.