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 1.37×106Da. ► This polysaccharide mainly consists of galactose. ► This polysaccharide showed significant effects on anti-tumor and immunomodulation. An acidic polysaccharide (GLSPs) with carbohydrate content of 72.06% and sulfate content of 6.13% was isolated from Gracilaria lemaneiformis. FTIR analysis of GLSPs showed that two typical absorptions appeared at 1259 and 804cm−1 were assigned to SO and COS bonds stretching respectively. HPGPC showed the molecular weight of GLSPs was mainly distributed at 1.37×106Da. GC analysis showed GLSPs was chiefly composed of galactose, and contained a small amount of rhamnose, arabinose, xylose and mannose. Moreover, the anti-tumor and immunomodulatory effects of GLSPs were evaluated in ICR mice transplanted H22 hepatoma cells. It was shown that GLSPs significantly inhibited the growth of tumor, promoted splenocytes proliferation and macrophage phagocytosis, and increased the level of IL-2 and CD8+ T cells in blood of tumor-bearing mice. The results suggested that GLSPs displayed remarkable anti-tumor and immunomodulatory activities, and it may provide a potential material of healthy food and clinical medicines.