ANTICOAGULANT PROPERTIES OF A FUCOIDAN FRACTION

Fucoidans are a family of high molecular weight sulphated polysaccharides in the Mr range 8 x 10(5)-10(6), widely dispersed in brown seaweed cell wall. When extracted from several brown algae, they exhibit anticoagulant properties. The chemical degradation of a crude extract, from Pelvetia canaliculata, was undertaken to obtain a low molecular weight polysaccharide (Mr 20,000 +/- 5,000) with the purpose of a possible clinical use. Its anticoagulant potency was investigated through the inhibition of factor IIa and factor Xa in the presence of antithrombin III or heparin cofactor II. The degraded fucoidan revealed a potent antithrombin activity: studied in an antithrombin III depleted plasma or in the presence of purified heparin cofactor II, the fucoidan was as efficient as heparin and dermatan sulphate on heparin cofactor II potentiation, at the same concentration by weight. In whole plasma or in the presence of the purified inhibitor, an anti-factor IIa activity mediated by antithrombin III was detected (30 times less potent than for heparin, on a weight to weight basis). In contrast, no anti-factor Xa activity was detected in the presence of the degraded fucoidan, under the same experimental conditions. These fucoidans, by-products of alginates preparation in the food and cosmetologic industries, are obtained easily. Thus, they may represent a cheap and easy source of a new type of anticoagulants.