Studies On The Purification Of Polysaccharides From Opuntia Dillenii Haw. And Its Antidiabetic Mechanism

Diabetes mellitus has become one of the broad endocrine diseases that threaten human health. Studies on the active polysaccharides lowering blood glucose from Opuntia dillenii Haw. provided a novel and safe way to prevent and cure diabetes. At present, there are few reports about the exact active components and antidabetic mechanism, of Opuntia dillenii Haw.The streptozotocin diabetic rats were given crude polysaccharides from Opuntia dillenii Haw. by intragastric administration. After several weeks, the intakes of food and water decreased, and the body weights were also lighter in diabetic mice. Blood glucose levels were determined every week, the effect of single administration was monitored in the first week, and glucose tolerance was determined after three weeks. All results showed that crude polysaccharides from Opuntia dillenii Haw. (ODCP) have hypoglycemic activity. The immune mechanism was studied, humoral immune responses and the function of phagocyte in diabetic rats were enhanced by ODCP. The results indicated that ODCP could improve immune function of diabetic mice remarkably; moreover, ODCP could modulate combination between insulin and its receptor, increase receptor sensitivity to insulin.Partial purification of polysaccharide from Opuntia dillenii Haw. was conducted: fresh cactus →crude polysaccharides extracted by hot water and then precipitated by ethanol→desalted with dialysis→fractionated by DEAE Sepharose fast flow ion-exchange column chromatography→separated by Sphadex G series molecular sieve column chromatography→freeze-drying. Three components were acquired through DEAE Sepharose fast flow column chromatography. Part I was subjected to chromatographyon the column of Sephadex G-75, Opuntia dillenii Haw. polysaccharide I (ODP1) and a protein were obtained. Part II was loaded onto the column of Sephadex G-200. Two constituents were eluted by their molecular size, and were named as ODP2 and ODP3 respectively. Part III was fractionated for the ODP4 and ODP5.Those polysaccharides were proved to be homogenous by electrophoresis. Molecular weight of ODP1, ODP2, ODP3, ODP4 and ODP5 were 2kDa, 1 044kDa, 4kDa, 915kDa and 5kDa respectively. The chemical composition was determined by high performance liquid chromatography. ODP1 was composed of rhamnose only, ODP2 was made up of rhamnose and glucose, ODP4 contained rhamnose and galactose, ODP3 and ODP5 were consisted of rhamnose and another unidentified monosaccharide respectively. But, the exact constituents of them need to be studied further.