Antitumor and immunomodulatory activity of polysaccharides from Sargassum fusiforme

► Anti-tumor activity of Sargassum fusiforme polysaccharide was evaluated. ► The polysaccharide could significantly inhibit the growth of A549 in mice. ► The polysaccharide had significantly toxicity effects on the A549 cell in vitro. ► The polysaccharide remarkably improve the immune response in A549-bearing mice. ► The study will be helpful to develop novel drugs and functional foods.