Background: Fucoidans are a group of sulfated fucose-rich polysaccharides that are isolated from brown marine algae and echinoderms, and recently have been found in seagrasses. Fucoidans, as well as their derivatives, have several beneficial biological effects and therapeutic potentials. In the present study, we aimed to evaluate the anticoagulative effects of two species of brown algae, namely Sargassum angustifolium (S. angustifolium) and Cystoseira indica (C. indica).
Methods: Fucoidan C and fucoidan S were extracted by an ethanol/water solvent system from S. angustifolium and C. indicia, respectively.  The anticoagulative effects of fucoidan C and fucoidan S were tested on 10 normal serum samples by evaluating the rate of thrombin time (PT) and prothrombin time (PTT).
Results: Both fucoidan C and fucoidan S significantly increased PTT. However, no significant difference was observed in PT. Fucoidan C had a greater effect on PTT prolongation compared with fucoidan S.
Conclusion: Both fucoidans extracted from S. angustifolium and C. indicia can be used as anticoagulants in biotechnology and human disorders.