Structural Characterization of a Homogeneous Polysaccharide Isolated from the Flower of Carthamus Tinctorius L. and Its Inhibitory Activity on HepG2 Proliferation

To isolate, purify and characterize the structure of polysaccharide from flowers of Carthamus tinctorius L., and to investigate the inhibitory effect of its homogeneous polysaccharide on the proliferation of HepG2 hepatoma cells. The polysaccharides in flowers of Carthamus tinctorius L. were extracted by water extraction and alcohol precipitation. The crude polysaccharides were separated and purified by anion exchange column and molecular sieve gel column. The homogeneity and molecular weight distribution were determined by high performance gel permeation chromatography(HPGPC). Its structure was elucidated by monosaccharide composition, methylation, and nuclear magnetic resonance(NMR) methods. The inhibitory effect of flowers of Carthamus tinctorius L. polysaccharide on tumor cells was studied by in vitro cell experiments. A homogeneous polysaccharide(CTPS-1A) was obtained. The molecular weight of CTPS-1A was 53800. The monosaccharide composition of CTPS-1A was analyzed by gas chromatography-mass spectrometer(GC-MS) and the monosaccharide composition was n(arabinose): n(galactose)=59.2:40.8. By methylation analysis, the glycosidic linkages were T-Galp, 1,3-Galp, 1,6-Galp, 1,3,6-Galp, T-Araf, 1,5-Araf, and 1,3,5-Araf. The results showed that CTPS-1A was an arabinogalactan(AG), its main chain was composed of -beta-Galp-(6 -> 1)-beta-Galp-(6 ->, and T-beta-Galp, 1,3-beta-Galp, T-alpha-Araf, 1,5-alpha-Araf, 1,3,5-alpha-Araf were connected to the 3 position of 1,3,6-Galp. The results of in vitro culture of HepG2 cells showed that CTPS-1A inhibited the growth of HepG2 by enhancing nuclear contraction and apoptosis.