Purification, antitumour and immunomodulatory activity of water-extractable and alkali-extractable polysaccharides from Solanum nigrum L.

The water-extractable and the alkali-extractable polysaccharides from Solanum nigrum L. (named SNLWP and SNLAP, respectively) and their four polysaccharide sub-fractions (SNLWP-1, SNLWP-2, SNLAP-1 and SNLAP-2), were isolated and purified by ethanol precipitation, dialysis, anion-exchange and gel filtration chromatography. Antitumour and immunomodulatory activity of the polysaccharides was evaluated by determining the survival time, the ascites volume, the weight of immune organ and the level of cytokine (IL-2, IL-10 and IFN-γ) of H22-bearing mice, respectively. The results showed that SNLWP-1, SNLAP-1 and SNLAP-2 had significant antitumour and immunomodulatory activity, whereas SNLWP-2 hardly demonstrated the activity. SNLWP-1 contained galactose and arabinose as main sugar components, and both SNLAP-1 and SNLAP-2 were rich in xylose, galactose and arabinose. SNLWP-2 was rich in glucose. In conclusion, SNLWP-1, SNLAP-1 and SNLAP-2 have potent antitumour activity which may be associated with their potent immunostimulating effect and monosaccharide composition.