Purification, Preliminary Structure and Antitumor Activity of Exopolysaccharide Produced by Streptococcus thermophilus CH9.

In the present study, the preliminary structure and in vitro antitumor activity of three exopolysaccharides (EPSs) from Streptococcus thermophilus CH9 were investigated. Then, three purified fractions of EPS-1a, EPS-2a, and EPS-3a were obtained by chromatography using DEAE-52 cellulose and Sephadex G-100, respectively. The average molecular weight of EPS-1a, EPS-2a, and EPS-3a, were 1.80 × 106, 1.06 × 106 and 1.05 × 106. The monosaccharide composition of EPS-3a was dramatically different from the others. The EPS-1a and EPS-2a were mainly composed of mannose, in a ratio of 69.82% and 57.09%, respectively, while EPS-3a was mainly composed of glucose (63.93%), without mannose. In addition, the surface morphology observed suggested that there were protein particles on the sugar chain of EPS-3a and EPS-3a was a protein-containing polysaccharide. Furthermore, EPS-3a exhibited higher antitumor activity against human liver cancer HepG2 cells in vitro. The antitumor activity of EPS-3a in HepG2 cells was associated with cell apoptosis. HE staining and Hoechst 33342 staining showed that with the treatment of EPS-3a, HepG2 cells had typical morphological changes. Flow cytometry analysis showed that the cell cycle was arrested at G0/G1 phase.

Structural characterization of an acid polysaccharide from Pinellia ternata and its induction effect on apoptosis of Hep G2 cells.

In the present study, a polysaccharide fraction (PTP) was isolated and purified from the tubers of Pinellia ternata. We researched its structure and anti-tumor activity, and further studied its molecular mechanism of inducing apoptosis of Hep G2 cells. The results indicated that PTP was an acid heteropolysaccharide and the average molecular weight of PTP identified by HPGPC was 3.06 × 106 Da. Ion chromatography (IC) determined that PTP was mainly composed of Ara:Gal:Glu:Man:GlcA:GalA in a molar ratio of 6.98:16.56:7.25:2.04:1:4.16. Combined with the results of FT-IR and NMR spectroscopy, it was found that PTP is a pyranose containing α-configuration and ß-configuration, mainly consist of ß-D-Gal, α-D-Glu, α-D-Ara and ß-D-Man. By analyzing the results of MTT, cell cycle, Annexin V-FITC/PI double staining and cell morphology observation, we concluded that PTP induced dose-dependent apoptosis of Hep G2 cells via S phase arrest. In addition, mitochondrial membrane potential detection and Western blot further indicated that PTP was capable of inducing apoptosis in Hep G2 cells through an endogenous mitochondria-mediated apoptotic pathway.