Partial characterization and anti-tumor activity of an acidic polysaccharide from Gracilaria lemaneiformis

► An acidic polysaccharide with high content of sulfate was obtained. ► The molecular weight of the polysaccharide is chiefly distributed at 1.37 × 106 Da. ► This polysaccharide mainly consists of galactose. ► This polysaccharide showed significant effects on anti-tumor and immunomodulation.