Anticoagulant potential of sulfated galactofucan from Turbinaria ornata: Targeting coagulation pathways and thrombin signaling in human umbilical vein endothelial cells.

Dysregulation of blood coagulation can result in thrombosis, highlighting the importance of anticoagulants that target both the extrinsic and intrinsic pathways of fibrin clot formation. This study explores anticoagulant effects of TOSP-3, a sulfated polysaccharide characterized as [→3)-4-O-SO₃-α-Fucp-(1 → 3)-4-O-SO₃-β-Galp-(1→] from the brown seaweed Turbinaria ornata, composed of sulfated α-(1 → 3)-fucopyranose (Fucp) and β-(1 → 3)-galactopyranose (Galp) units. In vitro analysis revealed that TOSP-3 (25 μg/mL) markedly extended activated partial thromboplastin time (100.49 s) and prothrombin time (77.57 s), highlighting its regulation on both intrinsic and extrinsic coagulation cascades. TOSP-3 induced a substantial reduction in coagulation factor Xa (FXa) expression (89 %) in human umbilical vein endothelial cells. It further exhibited a substantial five-fold inhibition of thrombin-catalyzed fibrin polymerization and reduced platelet aggregation by approximately 87 %, compared to the negative control (10 μM ADP). TOSP-3 attenuated thrombin-induced intracellular Ca2+ mobilization (∼33 %), while concurrently diminishing total thrombin production (33 %), thereby highlighting its inhibitory effects on thrombin-mediated signaling pathways. The sulfate content, structural patterns, and linkage characteristics of TOSP-3 may enable it to inhibit FXa expression and suppress thrombin-catalyzed fibrin polymerization through electrostatic interactions, potentially offering more effective modulation of the coagulation cascade than heparin. These findings highlight the potential of TOSP-3 as a natural anticoagulant for attenuating thrombotic disorders.