A　novel　polysaccharide　WPS-2-1,　with　an　average　molecular　weight　of　80　kDa,　was　purified　from　aqueous　extracts　of　Laminaria　japonica.　Monosaccharides　analysis　revealed　that　WPS-2-1　was　composed　of　mannose,　rhamnose　and　fucose　with　a　molar　ratio　of　1.0:2.3:1.2.　Analysis　by　periodate　oxidation-Smith　degradation　indicated　that　WPS-2-1　had　a　backbone　of　array　by　(1　-＞　4)-glycosidic　linkages.　Cytotoxicity　assay　showed　that　WPS-2-1　presented　significantly　higher　antitumor　activities　against　A375　and　BGC823　cells　with　a　dose-dependent　manner,　and　exhibited　lower　cytotoxicity　to　vascular　smooth　muscle　cells.　The　results　suggested　that　WPS-2-1　should　be　explored　as　a　potential　antitumor　agent　with　low　toxicity.　(C)　2012　Elsevier　Ltd.　All　rights　reserved.