Characterization of Lycium barbarum polysaccharide and its effect on human hepatoma cells

To investigate structure–bioactivity relationship of LBP, Lycium barbarum polysaccharide (LBP) was extracted and separated into five fractions using ultrafiltration membrane method. Then the effects of these polysaccharide fractions on human liver cancer cells (SMMC-7721) were observed by MTT assay, LSCM and FCM. And the components, molecular weight and conformation of LBP fractions were analyzed by GC, HPLC and AFM. The results showed that LBP-a8, LBP-a3, LBP-a1 and LBP-a4 could inhibit the proliferation of SMMC-7721 cells in a concentration and time dependent manner. But LBP-p8 could promote the growth of SMMC-7721 cells. LBP-a4 (10.2 kDa), which consists of uronic acid (11.5%), protein (0.34%) and neutral sugar (39.02%), could arrest SMMC-7721 cells at G0/G1 phase and enhance the intracellular Ca2+ concentration significantly. Nevertheless, LBP-p8 (6.50 × 103 kDa), which consists of uronic acid (13.4%), protein (4.77%) and neutral sugar (26.26%), did not change the cell cycle and Ca2+ concentration in cytoplasm significantly. The molecular conformation of LBP-a4 and LBP-p8 was spherical and flocculent molecular shape, respectively, suggesting that spherical molecular shape was benefit to LBP's apoptosis inducing activity while flocculent molecular shape did not have that function.