Composition and cytotoxicity of a novel polysaccharide from brown alga (Laminaria japonica)

► A water-soluble polysaccharide WPS-2-1 was purified from Laminaria japonica. ► WPS-2-1 was composed of mannose, rhamnose and fucose. ► WPS-2-1 had a backbone of array by (1 → 4)-glycosidic linkages. ► WPS-2-1 exhibited higher antitumor activities and lower cytotoxicity on VSMCs. ► WPS-2-1 may be considered as a potential candidate for antitumor agent.