We have developed an antibody-based method to assess plasma uptake of a proprietary Undaria-derived fucoidan galactofucan sulfate (GFS(TM)) after oral ingestion by human volunteers. Fucoidans have high-molecular-weights but exert biological effects in experimental animals after oral intake. By using a novel antibody raised against sulfated polysaccharides, we carried out a competitive ELISA to quantitate GFS in plasma samples from healthy volunteers who ingested 3 g/day of whole Undaria containing 10% GFS fucoidan, purified 75% GFS fucoidan, or 3 g of a nonsulfated placebo polysaccharide over 12 days. Increased reactivity to the novel antibody, as measured against preingestion levels, was detected at all time points. Assuming the measured material to be intact GFS, the concentration detected (median) was 4.002 and 12.989 mg/l when 3 g of 10% or 75% pure fucoidan was ingested orally over a period of 12 days, respectively. High-molecular-weight fucoidan can be detected in plasma using an ELISA competitive assay based on a novel antibody to sulfated polysaccharides.

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Seaweed-derived heparin-like substances such as fucoidan have been extensively studied in vitro as potential blood anticoagulants. However, there have been no human studies investigating the anticoagulant activity of fucoidan when administered orally. This pilot clinical trial was aimed to assess the safety and clinical effects of fucoidan ingestion on hemostasis as well as study its in-vitro anticoagulant activity. In a single-blinded clinical trial, a total of 20 human volunteers were allocated to both the placebo group (n = 10) who ingested 3 g of guar gum capsules and to the active treatment group (n = 10) who ingested 3 g of 75% fucoidan capsules for 12 days. Platelet indices, activated partial thromboplastin time, antithrombin-III, thrombin time, prothrombin time, and antifactor-Xa were analyzed according to standard methods. In vivo, activated partial thromboplastin time increased from 28.41 to 34.01 s (n = 10, P = 0.01), thrombin time decreased from 18.62 to 17.55 s (n = 10, P = 0.04), and antithrombin-III increased from 113.5 to 117% (n = 10, P = 0.03). The in-vitro fucoidan anticoagulant activity was found prominent. It increased activated partial thromboplastin time, thrombin time, and prothrombin time, whereas antithrombin-III decreased. In-vivo effect of fucoidan on hemostasis was not obvious probably due to low intestinal absorption. Thus, fucoidan in the form used in this study does not seem to have an oral anticoagulant activity, but it has a very strong in-vitro anticoagulant activity.