Chitosan Sulfated Product Synthesis, And Its Anticoagulant Properties

Chitosan is a biopolymer and consists of β(1â†'4)-2-amino-2-deoxy-D-glucose repeat units. It is normally obtained by the alkaline deacetylation of chitin, which is the second most abundant, naturally occurring structural material found in the shells of crustacean and cuticles of incects and also in the cell walls of some fungi and microorganisms. The sulfation of chitosan is the most interesting field of its chemical modification, since chitosan has the similar structure with heparin, which is of high antithrombin activity and is popularily used in medical field. Moreover, instead of heparin, the using of chitosan haparinoids can reduce the risk of contamination. Therefore, our work was carried out to investigate and determinate the optimum reactive condition of sulfated chitosan. The structure of sulfated chitosan was charactered by IR spectra. From its antithrombin activities, we studied its antithrombin mechanism and reached a qualitative conclusion. The main achievements our work had obtained were as follows:1. The chitosan with high DD (degree of deacetylation) ranging from 83.45% to 99.76% can be obtained by the method of interval washing with NaOH and the molecular weight of chitosan was scarcely affected.2. The method of H₂O₂ degradation didn't influence the degree of deacetylation of chitosan; the molecular weight of degraded chitosan was ranging from 328,700 to 64,000.3. The optimum synthenic condition of sulfated chitosan reaction of chitosan was about 8 hours, 35℃ and H₂SO₄:HSO₃Cl (V:V) was 1:2, this sulfated chitosan had the highest S-content,4. The result of IR spectrum showed that the sulfated chitosan is 6-O-sulfated chitosan and its main structure had something in common with the heparin.5. Explore elementarily the mechanism of the reaction between H₂SO₄/HSO₃Cl and chitosan.6. The 6-0 sulfated chitosan showed antithrombin activities in vitry by TT (thrombin time) investigation and the best antithrombin activity was 24.3U/mg, though it was less than equivalent heparin and the does of the heparinoid could be easily controlled. Moreover, we can deduce from the fact of lengthened-TT that the mechanism of antithrombin activity of chitosan was to combine with AT—HI to restrain the activities of FKa, IXa and II a, therefore , the TT can be able to be lengthened.7. The relationship between structrare of the 6-O sulfated chitosan and the antithrombin activities had been investigated as follows: a) The antithrombin activity tendency of the sulfated chitosans with same DD showed as 110.5KD>32.3KD>78.7KD b) the DD of the sulfated chitosans had obvious influences on the antithrombin activities when the molecular weight of the samples did't varied. The tendency was 93.45%>83.45%>77.65%...