Studies On Conditions Of Xylan Sulfation And The Anticoagulant Activity Of Sulfated Xylan

Polysaccharides, with many kinds of biological activities, such as antitumor,antivirus, anti-oxidant, can enhance the function of immune system, and so on. Moreand more attention has been paid to study on polysaccharide. Especially manypolysaccharide sulfates have anticoagulant activity and anti-HIV activity, so itparticularly attracts attention.Xylan from corn cobs is the main kind of material to producexylooligosaccharide, and it's derivatives have many kinds of biological activities. Theisolation of corn cob xylan, the sulfated reaction condition of water insoluble xylan,the anticoagulant activity of xylan sulfate, and the anticoagulant mechanism werestudied in this paper. Water soluble xylan (wsX) and water insoluble xylan (wisX)were separated from corn cobs by alkali extraction method. The mass ratio of wsXand wisX in the xylan obtained in the experiment was 1:2, and the monosaccharideanalysis showed that the main composition of them was xylose. Sulfation of wisXwith chlorosulfonic acid-pyridine through single factor and thogonal test , was studied.The result showed that the optimum condition for temperature, the molar ratio ofchlorosulfonic acid to pyridine, and the reaction time were 80℃, 1:2, and 6h,respectively. In this conditions, the sulfated polysaccharide was obtained with averagemolecular mass 1.0×10~5 , degree of sulphate substitution 1.62. The white, floc, watersoluble solid was got by purification with DEAE Sepharose Fast Flow anion exchangechromatography. The ultraviolet spectrum of the xylan sulphate showed newabsorption at 282nm. The infrared spectrum of it showed intensive absorption at1256cm-1 and 814 cm-1 attributed to the stretching of S=O bond and C-O-S bonds onthe sulfate ester of the hexose respectively.The study showed that the xylan sulphate,wisX-S6,displayed some anticoagulantactivity with activated partial thromboplastin time(APTT), prothrombin time (PT) andthrombin time (TT) test. In the test, APTT and TT were markedly prolonged bywisX-S6 and it was suggested that wisX-S6 influenced blood clotting in intrinsicpathway and common pathway respectively. Its mechanism was also presumed thatwisX-S6 bound to antithrombin (ATIII), and activated ATIII, then the thrombinactivity was inhibited by acute ATIII, which converted from chronic ATIII. In additionwisX-S6 could prolong the fibrinogen clotting time. Its function was suggested thatwisX-S6 combined to fibrinogen , and then blocked its binding site to thrombin orchanged the conformation of fibrinogen. The inhibit ratio of maximum plateletaggregation was 4.8% at concentration of 5μg/mL without side-effect on bleeding.In this paper the relationship between wisX-S6 structure and anticoagulantactivity, including degree of substitute, molecular mass and monosaccharidecomponent of side chain, was studied. The sulfonic group, introduced with sulphatedreaction, was the main active part. There was direct correlation between anticoagulantactivity and concentration of sulfonic group as the degree of substitution was above0.8. It was found that there was not direct correlation between anticoagulant activityand molecular weight, but the activity would be lost when the molecular weight wasless than 10,000. The anticoagulant activity was enhanced when the side chain wascomposed of glucuronic acid or acetyl. So the activity would be influenced by the sidechain of the xylan sulphate.