自由基氧化法制备海带岩藻聚糖硫酸酯的抗凝血活性

以海带(Laminaria japonica)为原料,采用阴离子交换和自由基氧化降解反应制备了不同分子量和硫酸根含量的岩藻聚糖硫酸酯,然后以血浆复钙时间(RT)、活化部分凝血活酶时间(APTT)、凝血酶原时间(PT)、凝血酶时间(TT)为指标,研究海带岩藻聚糖硫酸酯抗凝血活性的构效关系.结果表明,采用离子交换,可从海带糖提取物中分离出低硫大分子组分F-A和高硫大分子组分F-B.粗糖经自由基氧化降解,可得到分子量为1.5 kD和8.0 kD左右的低分子组分,实验重复性好,产物分子量集中,其中分子量8.0 kD左右的低分子组分硫酸根含量最高.抗凝血实验表明,岩藻聚糖硫酸酯能显著延长RT、APTT和TT,尤以高硫组分大分子F-B抗凝血效果最好,而对PT影响不大,说明岩藻聚糖硫酸酯对外源凝血系统影响很小,它的抗凝血活性主要是通过内源性凝血途径来实现的.岩藻聚糖硫酸酯分子量对抗凝血活性的影响要比硫酸根含量的影响更大,其抗凝血活性随着分子量的降低而显著降低.对于分子量相近的岩藻聚糖硫酸脂,硫酸根含量越高,则抗凝血活性越高.总之,岩藻聚糖硫酸酯分子量和硫酸根含量越高,其抗凝活性越高.

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.