Characterization and anti-tumor activity of alkali-extracted polysaccharide from Enteromorpha intestinalis

The polysaccharide DAEB was isolated and purified from Enteromorpha intestinalis. It consisted of rhamnose, xylose, galactose, and glucose in a molar ratio of 5.36:1.00:0.57:0.64, and had a molecular weight of 46.8 kDa. Mice were treated with three doses of DAEB for 10 consecutive days by oral administration, the tumor inhibition was 61.17%, 67.65% and 70.59% at doses of 100, 200 and 400 mg/kg, respectively. However, no direct cytotoxicity was detected. At dose of 100, 200 and 400 mg/kg, a significant increase (P < 0.01) in relative spleen and thymus weight, and production of tumor necrosis factor α (TNF-α) were observed in DAEB treated groups. We also found that DAEB significantly stimulated lymphocyte proliferation, especially Concanavalin A-induced lymphocyte proliferation in a dose-dependent manner, and augmented phagocytosis and secretion of NO and TNF-α in peritoneal macrophages. The results indicated that DAEB had potent anti-tumor activity which may be associated with its potent immunostimulating effect.