In Vitro Anticoagulant Effects of Fucoidan-Rich Extracts from South African Brown Macroalgae

Blood coagulation is a vital physiological process; however, its dysregulation may result in excessive clotting and adverse health outcomes. Current anticoagulant therapies, such as heparin, are commonly employed to prevent and treat thrombosis, but these agents have notable limitations, including poor oral bioavailability and the risk of haemorrhage. Therefore, there is growing interest in discovering alternative natural compounds with anticoagulant properties. This study investigated the in vitro anticoagulant potential of previously characterised fucoidan-rich extracts from three South African brown seaweed species, namely Ecklonia maxima, Ecklonia radiata, and Sargassum incisifolium. Anticoagulant activity was evaluated using prothrombin time (PT), activated partial thromboplastin time (aPTT), and thrombin-induced clotting using FIB-C reagent; D-dimer was assessed separately as an exploratory endpoint. Mean PT and aPTT increased across the tested extract concentration ranges. At 350 µg·mL⁻¹, E. maxima and E. radiata produced PT values 4.13 and 3.95 times the control value, respectively; both exceeded S. incisifolium but did not differ significantly from one another. Among the extracts, E. maxima produced the highest mean aPTT response, reaching 2.61 times the control value at 50 µg·mL⁻¹. Thrombin-induced clotting times measured with the FIB-C reagent were prolonged at the highest tested concentration for each preparation, with responses varying among preparations and concentrations. Together, the coagulation assays support the in vitro anticoagulant potential of these fucoidan-rich extracts, while their specific mechanisms of action remain to be determined.