Structural Characterization and Anticoagulant Activity of Oligosaccharides Derived from Sargassum fusiforme Fucoidan

In order to study the anticoagulant oligosaccharides derived from Sargassum fusiforme fucoidan (SFF), the monosaccharide composition, molecular mass and physicochemical characteristics of SFF were determined by high performance liquid chromatography (HPLC), high performance gel permeation chromatography (HPGPC) and chemical methods, respectively. Degradation of SFF was carried out using hydrochloric acid (HCl). The degradation products were separated by gel permeation chromatography on Bio-gel P4. The anticoagulant activity of the resultant oligosaccharide fractions was evaluated by activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) assays. The oligosaccharide fraction with the highest anticoagulant activity and lower molecular mass was selected and its structural characteristics were analyzed by negative-ion electrospray mass spectrometry (ES-MS). Results indicated that SFF mainly consisted of fucose, galactose, mannose and glucose in a molar ratio of 67.11:26.69:2.54:3.66. The average molecular mass of SFF was 708 kDa and the contents of total sugar, protein and sulfate ester in it were 56.44%, 1.14% and 26.22%, respectively. Five oligosaccharide fractions, named P1 to P5, were obtained by degradation of SFF with hydrochloric acid. They all could prolong the APTT and fractions P1, P2 and P3 were more effective than P4 and P5, especially P3; however they were ineffective in prolonging TT or PT. P3, a highly pure oligosaccharide, was mainly composed of Fuc₃(SO₄)₂.