In this study, sulfated polysaccharide-rich extracts were isolated from 22 tropical seaweeds (4 red, 11 brown, and 7 green) found in northeastern Brazil, and evaluated for the role of anticoagulant agents.

Udoteaflabellum (a green seaweed) extract was the most potent, requiring an amount of only 3 µg to double the plasma coagulation time in the activated partial thromboplastin time test. A similar result was obtained with 1 µg of heparin.

Two sulfated homoglycans with anticoagulant activity, F-I (130 kDa) and F-II (75 kDa), were isolated from this extract using several bio-guided purification steps. Their anticoagulant activity, as well as properties related to the antitumor activity (anti-proliferative, anti-adhesive, and anti-migratory), were accessed.

The anticoagulant activity

Their anticoagulant activities were close to that of heparin. The researcher found that F-I and F-II (0.5–10 μg/mL) were not able to directly inhibit thrombin. In the presence of anti-thrombin, F-I (0.5 μg/mL) was more effective than heparin (0.5 μg/mL) in inhibiting thrombin, while F-II showed similar effects as heparin.

F-I and F-II also inhibited B16-F10 (murine melanoma cells) adhesion, migration, and proliferation on a fibronectin-coated surface, but not on laminin- or collagen I-coated surfaces.

Except for the antiproliferative activity, the other effects of F-I and F-II were eliminated upon their desulfation (~50%), indicating that the degree of sulfation is not as important for F-I and F-II anti-proliferative activity as the sulfation position.

Taken together, the results provide strong evidence for the potential utility of sulfated galactans from U. flabellum, making these compounds an interesting option for future investigations that aim to design new anticoagulant/antitumor agents.

the researchers obtained 15 anticoagulant sulfated polysaccharide-rich extracts from tropical seaweeds. Among these, Udotea flabellum extract was the most potent. Two sulfated homoglycans, F-I (130 kDa) and F-II (75 kDa), with anticoagulant activity were isolated from this extract through several bio-guided purification steps.

Although F-II had a higher content of sulfate groups than F-I, the activities of both polysaccharides were similar across all tests. The anticoagulant activity of these polysaccharides depends mainly on their ability to potentiate the AT inhibitory action. F-I and F-II also inhibited B16-F10 cell adhesion, migration, and proliferation on a fibronectin-coated surface, but not on laminin- or collagen I-coated surfaces.