A highly sulfated pyranosic (1„_3)-ƒÒ-L-arabinan with anticoagulante activity. Mechanism of action.

M. CIANCIA, P. V. FERNÁNDEZ, I. QUINTANA, A. S. CEREZO, J. M. ESTEVEZ

Congreso; 16th European Carbohydrate Symposium,; 2011

The room temperature water extract obtained from green seaweed Codium vermilara1 was fractionated by addition of KCl to give solutions of increasing concentrations of this salt. Only one insoluble product was obtained at 0.115 M (Ab) in 31% yield which contained 97% of L-arabinose, a sulfate/arabinose molar ratio of 1.8/1, an [α]D = + 167.5 º, and a number average molecular weight of 100 KDa. Methylation analysis of Ab and its desulfated derivative (Dab) showed that this polysaccharide is mainly constituted by 3-linked disulfated  arabinopyranosyl residues, although some mono- and non-sulfated units are also present. Analysis of the corresponding NMR spectra confirmed this structure and showed that these units are in the β–configuration. This product showed a high anticoagulant activity, but lower than that of heparin, as 5 and 0.65 mg/ml respectively were necessary to increase the thrombin time in 2.5 times. The main coagulation mechanism is though the direct inhibition of thrombin, although inhibition of thrombin by potentiation of antithrombin and heparin cofactor II was also found by amydolitic methods. In conclusion, a highly sulfated pyranosic β-l-arabinan was isolated from the cell walls of a green seaweed. It showed anticoagulant behaviour by a mechanism different to that of heparin. To the best of our knowledge, this is the first report in nature of a polysaccharide constituted only by arabinose residues in the pyranosic form.