RESUMO
The major acidic polysaccharide from the brown alga Laminaria cichorioides is a complex and heterogeneous sulfated fucan. Its preponderant structure is a 2,3-disulfated, 4-linked alpha-fucose unit. The purified polysaccharide has a potent anticoagulant activity, as estimated by APTT assay ( approximately 40 IU/mg), which is mainly mediated by thrombin inhibition by heparin cofactor II. It also accelerates thrombin and factor Xa inhibition by antithrombin but at a lower potency. Sulfated fucan from L. cichorioides is a promising anticoagulant polysaccharide and a possible alternative for an antithrombotic compound due to its preferential heparin cofactor II-dependent activity.
Assuntos
Anticoagulantes/química , Cofator II da Heparina/química , Heparina/química , Laminaria/metabolismo , Phaeophyceae/metabolismo , Animais , Testes de Coagulação Sanguínea , Cromatografia por Troca Iônica/métodos , Relação Dose-Resposta a Droga , Fator Xa/química , Humanos , Espectroscopia de Ressonância Magnética , Polissacarídeos/química , Frações Subcelulares/química , Trombina/químicaRESUMO
An acidic polysaccharide with anticoagulant activity was isolated from the edible mushroom Auricularia auricula using water, alkali or acid extracts. The alkali extract showed the highest anticoagulant activity and was thereby further purified using gel filtration chromatography. Specific anticoagulant activity of the purified polysaccharide was 2 IU/mg and its average mass was approximately 160 kDa. The polysaccharide from this species of mushroom contains mainly mannose, glucose, glucuronic acid and xylose but no sulfate esters. Its anticoagulant activity was due to catalysis of thrombin inhibition by antithrombin but not by heparin cofactor II. Inhibition of Factor Xa by antithrombin was not catalyzed by the polysaccharide. The glucuronic acid residues were essential for the anticoagulant action of the mushroom polysaccharide since the activity disappeared after reduction of its carboxyl groups. In ex vivo tests using rats orally fed with the polysaccharide, we observed an inhibitory effect on platelet aggregation as observed with aspirin, a well-known antiplatelet agent. The polysaccharides from these mushrooms may constitute a new source of compounds with action on coagulation, platelet aggregation and, perhaps, on thrombosis.
Assuntos
Anticoagulantes/farmacologia , Antitrombinas/fisiologia , Basidiomycota/química , Polissacarídeos/farmacologia , Animais , Anticoagulantes/isolamento & purificação , Antitrombinas/farmacologia , Coagulação Sanguínea/efeitos dos fármacos , Cromatografia em Gel , Ácidos Hexurônicos/análise , Coreia (Geográfico) , Masculino , Monossacarídeos/análise , Tempo de Tromboplastina Parcial , Plantas Comestíveis , Polissacarídeos/química , Polissacarídeos/isolamento & purificação , Tempo de Protrombina , Ratos , Ratos Sprague-DawleyRESUMO
We searched for polysaccharides with anticoagulant activity and inhibitory action on platelet aggregation induced by collagen in 59 species of medicinal plants. We then concentrated our studies on the polysaccharide from the species Porana volubilis, which showed the highest anticoagulant activity among the plants tested. The polysaccharide from this species has an average molecular mass of approximately 10 kDa, contains mainly galactose, galacturonic acid, and mannose but no sulfate esters. Its anticoagulant activity is mediated by the enhancement of thrombin inhibition that in turn is mediated by heparin cofactor II but not by antithrombin. The galacturonic acid residues are essential for activity since after reduction of its carboxyl groups the anticoagulant activity disappears. Our report is the first description of a natural nonsulfated polysaccharide from higher plants with anticoagulant activity, which may constitute a new source of compounds with action on coagulation and, perhaps, on thrombosis.