Catalytic synthesis and antitumor activities of sulfated polysaccharide from Gynostemma pentaphyllum Makino

A native polysaccharides (GPP2) was isolated from Gynostemma pentaphyllum Makino. Four sulfated derivatives of GPP2 (GPP2-s1 to s4) were prepared by chlorosulfonic acid method with ionic liquids (ILs) as solvent and 4-dimethylaminopyridine (DMAP) as catalyst. The structures of the sulfated derivatives were analyzed by FT-IR spectra and 13C NMR spectra, which indicated that the sulfated groups were introduced mainly at the C-6 position as well as at the C-2 position. The products showed different degree of substitution (DS) ranging from 0.79 to 1.34, and different weight-average molecular mass (Mw) ranging from 8.64 to 11.2 Da. The sulfated derivatives inhibited the growth of HepG2 cells and Hela cells in vitro significantly. Furthermore, they had no obvious influence on 293 cells, which indicated that they had low toxicity. Flow cytometric studies revealed that treatment of the sulfated derivatives with Hela cells could mediate the cell-cycle arrest in the S phase.