The polyphenolic-polysaccharide complex of Agrimonia eupatoria L. as an indirect thrombin inhibitor - isolation and chemical characterization.

The polyphenolic-polysaccharide complex was isolated from the dried aerial parts of the medicinal plant Agrimonia eupatoria L. using a multi-step process involving the degreasing of the plant material by extraction with organic solvents, followed by extraction with hot alkali, neutralization, further separation with organic solvents and dialysis. The complex was homogeneous with a molecular weight of about 55 × 103 g/mol and consisted mainly of carbohydrates and polyphenols matrix, composed of lignin-related units, with the dominance of dimethoxyphenyl structures. The carbohydrate moiety consists mostly of arabinogalactan associated with highly esterified rhamnogalacturonan. In vitro anticoagulant studies revealed the ability of the A. eupatoria complex to inhibit plasma clot formation, mainly in the intrinsic pathway of the blood coagulation cascade. Further studies on the mechanisms of this anticoagulant activity revealed that the isolate was primarily an indirect inhibitor of thrombin, mediated by antithrombin or by heparin cofactor II. Such mechanism of action is characteristic for highly sulfated glycosaminoglycans.