Sulfated polysaccharides SpvF1, SpvF2, SpvF3, and SpvF4 from the brown alga S. vietnamense collected north of Hon Do (Nha Trang Bay, Vietnam) were isolated and studied. The structure of the obtained polysaccharide was studied using chemical methods and NMR spectroscopy. Fucoidans were low-sulfated (SpvF1, SpvF2) and medium-sulfated (SpvF3, SpvF4) heterogeneous polysaccharides. The molecular weight of the polysaccharides obtained was in the range of 16 to 44 kDa. All investigated fucoidans until 400 µg/mL were not cytotoxic for human colon carcinoma cells DLD-1, HCT-116, and HT-29 in vitro. Fucoidans SpvF1 and SpvF2 have inhibited the colony formation and growth of investigated cells from 20 to 30%. Fucoidans SpvF3 and SpvF4 have the strongest inhibitory effect for investigated cancer cells: from 40 to 50%.
