[Anticoagulant activity of fucoidans from brown algae]

The anticoagulant activity of polysaccharide fucoidans from 11 species of brown algae was studied. The anticoagulant activity was measured by the activated partial thromboplastin time (APTT), prothrombin time and thrombin time. Inhibitory action of fucoidans varied significantly from one species to another. Fucoidans from Laminaria saccharina and Fucus distichus showed high anticoagulant activities, while fucoidans from Cladosiphon okamuranus and Analipus japonicus were almost inactive. The fucoidan inhibitory effect on thrombin and factor Xa in the presence or in the absence of natural thrombin inhibitor, antithrombin III (AT III), was also studied. In contrast to the best studied anticoagulant heparin the most of the fucoidans inhibited thrombin in the absence of AT III. In the presence of AT III inhibitory effect of fucoidans was increased considerably. Unlike heparin, the effect of fucoidans on factor Xa was very weak in the presence of AT III and was not observed in the absence of AT III. The correlation between the anticoagulant activities of this series of fucoidans and their anti-inflammatory action, studied by us earlier, was not found. It is expected that two these types of fucoidan activities depend on different structural features of fucoidans. These findings show the possibility to obtain fucoidans with high anti-inflammatory action and with low anticoagulant activity. Anticoagulant activity of the fucoidans did not depend on the content of fucose, the other neutral sugars and sulfates in the preparations, and also on the structure of the backbone of molecule. Taken together, these results indicate on prospects of fucoidan study as potential therapeutic agents.