en هماتولوژی و آنکولوژی Hematology & Oncology پژوهشي Research <div style="text-align: justify;"><strong>Background</strong>: 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 <em>Sargassum angustifolium (S. angustifolium)</em> and <em>Cystoseira indica</em> (C. <em>indica</em>).<br> <strong>Methods</strong>: Fucoidan C and fucoidan S were extracted by an ethanol/water solvent system from <em>S. angustifolium</em> and C. <em>indicia</em>, respectively. &nbsp;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).<br> <strong>Results</strong>: 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.<br> <strong>Conclusion</strong>: Both fucoidans extracted from <em>S. angustifolium</em> and C. <em>indicia</em> can be used as anticoagulants in biotechnology and human disorders.<br> &nbsp;</div> Fucoidan, Sargassum angustifolium, Cystoseira indica, Anticoagulation 125 132 http://rmm.mazums.ac.ir/browse.php?a_code=A-10-1099-3&slc_lang=en&sid=1 Narges Obeidi nobeidi@yahoo.com 10031947532846009040 10031947532846009040 Yes Department of Hematology, School of Para Medicine, Bushehr University of Medical Sciences, Bushehr, Iran. Mohammad Javad Mousavi sm-mousavi@razi.tums.ac.ir 10031947532846009041 10031947532846009041 No Department of Hematology, School of Para Medicine, Bushehr University of Medical Sciences, Bushehr, Iran. Arghavan Hosseinpouri a.hosseinpouri@gmail.com 10031947532846009042 10031947532846009042 No Department of Cellular and Molecular Sciences, Faculty of Sciences, Persian Gulf University, Bushehr, Iran. Hamideh Malekhayati hm.lab2@gmail.com 10031947532846009043 10031947532846009043 No Student Research Committee, Bushehr University of Medical Sciences, Bushehr, Iran. Elham Ehsandoost 10031947532846009044 10031947532846009044 No Department of Food Science & Technology, Shiraz University, Shiraz, Iran.