A pyruvylated and sulfated galactan from the green alga Dictyosphaeria cavernosa: Structure, anticoagulant property and inhibitory effect on zebrafish thrombosis

A pyruvylated and sulfated galactan from the green alga Dictyosphaeria cavernosa, designated PSG, was obtained by dilute alkali extraction, ion-exchange and gel filtration chromatography. The backbone of PSG was composed of 3-linked β-d-Galp units with partial sulfation on C-4 and C-6. Pyruvate ketals were linked to O-3 and O-4 of nonreducing terminal β-d-Galp, as well as O-4 and O-6 of 3-linked β-d-Galp. The branches consisting of 6-linked β-d-Galp(4SO4) and β-d-Galp(3,4-Pyr)-(1→ units were located at C-6 of 3-linked β-d-Galp unit. PSG possessed obvious anticoagulant effect in vitro as assessed by the tests of activated partial thromboplastin time and thrombin time. The assay of anticoagulant mechanism showed that PSG promoted thrombin inactivation mediated by heparin cofactor-II and antithrombin-III (ATIII), and could effectively potentiate factor Xa inactivation by ATIII. The antithrombotic activity of PSG in vivo was assessed by phenylhydrazine (PHZ)-induced zebrafish thrombotic model. The results indicated that PSG obviously reduced peripheral erythrocytes aggregation, enhanced cardiac blood flow and improved peripheral platelet circulation, and PSG possessed a marked inhibitory effect on the PHZ-induced zebrafish thrombosis. Thus, PSG is a hopeful anticoagulant and antithrombotic polysaccharide.