Preparation, preliminary characterization and inhibitory effect on human colon cancer HT-29 cells of an acidic polysaccharide fraction from Stachys floridana Schuttl. ex Benth.

A polysaccharide fraction (SFPSA) was obtained from the rhizomes of Stachys floridana Schuttl. ex Benth. by hot water extraction and sequential purification of anion-exchange chromatography and gel-filtration chromatography. SFPSA was found to be an acidic polysaccharide fraction with an average molecular weight of 168kDa and composed of rhamnose, glucuronic acid, galacturonic acid, glucose, galactose and arabinose in a molar percentage of 7.75:1.65:14.92:1.87:33.17:40.64, respectively. SFPSA could inhibit the proliferation and growth of human colon cancer HT-29 cells in a time- and dose-dependent manner within 48h, induce the apoptosis and increase the accumulation in G₂/M phase of HT-29 cells. Furthermore, it was found that SFPSA could decrease Bcl-2 mRNA level, and increase the mRNA expressions of Bax and p53 and the activity of caspase-3. These results indicated that SFPSA might induce apoptosis of HT-29 cells through regulation of apoptosis-associated gene expressions such as Bcl-2, Bax and p53 and the activation of caspase-3.