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

► Four homogeneous polysaccharides isolated from Solanum nigrum L. ► Three of them prolong the survival time of H22-bearing mice. ► They increase the weights of immune organ. ► They augment IL-2 and IFN-γ production and decrease IL-10 expression. ► They show antitumour and immunomodulatory activity.