Relationship between antithrombotic activities of fucans and their structure

A low molecular weight fucan fraction extracted from the brown seaweed Ascophyllum nodosum was previously shown to exhibit dose‐related venous antithrombotic activity with an ED 80 of about 20 mg/kg, 2 h after a single subcutaneous injection HCII (Colliec et al. [1991] Thromb Res 64:143–154; Mauray et al. [1995] Thromb Haemast 74:1280–1285). Its activity was comparable to that of a low molecular weight heparin (Dalteparin ® ). This fucan fraction is one of several, with a range of different structure parameters, prepared by degradation of the whole native fucan. These low molecular weight fractions were compared using a Wessler stasis thrombosis model in rabbits and by determination of their in vitro and ex vivo anticoagulant activities. Intravenous administrations of these fractions reduced thrombosis in a dose‐dependent manner. Partial removal of sulfate groups and/or partial degradation lead to a significant decrease in their anticoagulant and antithrombotic activities. The integrity of the regular pattern of sulphation of the fucoidan is necessary for antithrombotic activity. Drug Dev. Res. 51:216–224, 2000. © 2001 Wiley‐Liss, Inc.