Comparison of the anticoagulant action of sulfated and phosphorylated polysaccharides.

Oat spelts xylan (OSX), fucoidan, kappa carrageenan and chondroitin sulfates A and C were sulfated using chlorosulfonic acid-pyridine complex while the first three were phosphorylated using methane sulfonic acid-phosphorous pentoxide mixture. The compounds were isolated as the sodium salts and their in vitro anticoagulant properties were determined by measuring the concentration of each compound required to double prothrombin time of pooled normal human plasma. The results of 31P-nmr spectroscopy showed that phosphorylation significantly increased the molecular weights of the polysaccharides by forming phosphodiester and diphosphodiester bonds. In general the anticoagulant properties of the sulfated polysaccharides were related to the % sulfate while the phosphorylated polysaccharides showed increases in anticoagulant properties which were related to the increase in the molecular weight and inversely related to the % phosphate. The mechanism of action of oat spelts xylan phosphate (OSXP) was studied using 125I-thrombin and normal human plasma. The results showed that at lower concentration of the OSXP, the complexation of 125I-thrombin with heparin cofactor-II(HC-II) was enhanced, while at higher concentration of the compound, the complexation with both antithrombin-III(AT-III) and HC-II was enhanced.