Structural Characteristics and in vitro Antitumor Activity of Water-Soluble Polysaccharides from Brown Algae of the Russian Far East and Vietnam

Laminarans and fucoidans from two Russian Far-East ( Desmarestia viridis and Dictyota dichotoma ) and four Vietnam species ( Dictyota divaricata , Padina boryana , Sargassum duplicatum , and S. feldmannii ) of brown algae were isolated and studied. Water-soluble polysaccharides from D. divaricata , P. boryana , and S. feldmannii were mainly fucoidans; from D. viridis , D. dichotoma , and S. duplicatum , approximately equal amounts of laminarans and fucoidans. All studied laminarans had a main chain of 1,3-bonded glucose residues with branching on C-6 with various ratios of 1,3:1,6 bonds. Fucoidans from D. viridis and D. dichotoma were medium- and low-sulfated heterogeneous polysaccharides; from D. divaricata , P. boryana , S. duplicatum , and S. feldmannii , sulfated galactofucans containing traces of mannose, xylose, and glucose. Galactofucans from D. divaricata , P. boryana , S. duplicatum , and S. feldmannii were not cytotoxic and exhibited antitumor activity against DLD-1 human colon carcinoma cells.