Anticoagulant activity of fucoidans from Laminaria japonica by free radical oxygen degradation

Fucoidan is a kind of natural active polysacchardes containing sulfate group from brown algae and possesses excellent biological properties,including anticoagulant,anti-thrombosis and anti-tumor,antivirus,and so on.It is a very excellent natural resource for functional food and medicine.In this study,we attempted to determine the relationship between the chemical properties and the anticoagulant activity of fucoidan fractions from Laminaria japonica.Fucoidan fractions from Laminaria japonica with different molecular weight and sulfated ester content were prepared by ion-exchang;chromatography and free radical oxygen degradation and their anticoagulant activities were investigated by classical coagulation assays activated partial thromboplastin time(APTT),recalcification time(RT),prothrombin time(PT)and thrombin time(TT),using heparin as reference compound.By ion-exchange,two different large molecular weight fucoidan fractions,low sulfated F-A and highly sulfated F-B,were obtianed from the crude polysaccharides of Laminaria japonica.Two fractions with molecular weight of 1.5 kD and 8.0 kD were obtained by free radical oxygen degradation from large molecular weight crude fucoidan.The sulfated ester content of fraction with molecular weight of 8.0 kD was especially higher than that of F-B.This method was used in high yields and good reproducibility.Fucoidan,especially fraction with large molecular weight of 17.5 kD and high sulfated ester content of 33.5%,had significant activity in APTT,TT and RT,but without showing any effect in PT.This result indicates that fucoidan has an inhibition on the intrinsic and /or common system,but no effect on extrinsic part of coagulation system.The composition of fucoidan had influence on anticoagulant activity,especially the molecular weight was found to be a more critical factor than sulfated content.The anticoagulant activity of fucoidan significant decreaded with the decrease of molecualr weight.The more highly sulfated fucoidan fractions were found to affect the agulant time to a higher extent when evaluated on a weight basis.In general,the anticoagulant activity of fucoidan clearly increases with the increasing molecular weight and sulfated content.