Pelvitia canaliculata fucoidan is a fucan sulphate occurring in brown marine algae (Phaeophyta), typically Pelvitia canaliculata, and has been shown to have anti-coagulant activity. The fuicose content of this fucan is approx. 38.3% and it also contains galactose (approx. 5.6%), uronic acid (approx. 4.3%) and sulfate (approx. 43%).
A recent reference contains more information about the properties:
Fitton H. J., Stringer D. N. and Karpiniec S. S., Therapies from Fucoidan: An Update, Marine Drugs, 13, 5920-5946 (2015)