Fucoidan is a fucan sulfate occurring in brown marine algae (Phaeophyta, typically Ascophyllum nodosum and Laminaria digitata) and has been shown to have anti-coagulant activity. The main constituents are α(1-4) and α(1-2) linked L-fucose sulfates although galactose also occurs and there are many variations of the basic structure found in different species of Phaeophyta.