Isolation and antitumor activities of acidic polysaccharide from Gynostemma pentaphyllum Makino

► Gynostemma pentaphyllum is a well-known traditional Chinese herbal medicine. ► Two acidic polysaccharides (GP-B1 and GP-C1) were obtained from this medicinal herb. ► GP-B1 could suppress the growth of melanoma B16 in vivo and in vitro. ► GP-B1 increased serum TNF-α, IFN-γ, and IL-12 levels and reduced IL-10 production. ► The antitumor effects of GP-B1 are associated with immunostimulation.