New natural polysaccharides with potent antithrombic activity: fucans from brown algae.

Fucans extracted from brown algae exhibit anticoagulant properties, as demonstrated by coagulation assays and kinetic study of the inactivation of thrombin in the presence of antithrombin III. These derivatives exert a direct antithrombic activity by an antithrombin III-independent pathway. Besides, their anticoagulant activity is not mediated by a potency to inhibit factor Xa. Relatively low-molecular-mass fractions (50,000 Daltons) prepared by chromatographic fractionation of the crude fucans also exhibit anticoagulant activity. They may prove useful as anticoagulant drugs.