Structural Characteristics and Anticancer Activity of Fucoidan from the Brown Alga Sargassum mcclurei

Three different fucoidan fractions were isolated and purified from the brown alga, Sargassum mcclurei. The SmF1 and SmF2 fucoidans are sulfated heteropolysaccharides that contain fucose, galactose, mannose, xylose and glucose. The SmF3 fucoidan is highly sulfated (35%) galactofucan, and the main chain of the polysaccharide contains a -> 3)-alpha-L-Fucp(2,4SO(3)(-))-(1 -> 3)-alpha-L-Fucp(2,4SO(3)(-))-(1 -> motif with 1,4-linked 3-sulfated alpha-L-Fucp inserts and 6-linked galactose on reducing end. Possible branching points include the 1,2,6- or 1,3,6-linked galactose and/or 1,3,4-linked fucose residues that could be glycosylated with terminal beta-D-Galp residues or chains of alternating sulfated 1,3-linked alpha-L-Fucp and 1,4-linked beta-D-Galp residues, which have been identified in galactofucans for the first time. Both alpha-L-Fucp and beta-D-Galp residues are sulfated at C-2 and/or C-4 (and some C-6 of beta-D-Galp) and potentially the C-3 of terminal beta-D-Galp, 1,4-linked beta-D-Galp and 1,4-linked alpha-L-Fucp residues. All fucoidans fractions were less cytotoxic and displayed colony formation inhibition in colon cancer DLD-1 cells. Therefore, these fucoidan fractions are potential antitumor agents.