Extraction, Isolation And Biological Properties Of Polysaccharides From Purple Sweet Potato

Polysaccharides are widely distributed in the world, mainly obtained from plants, animals, microorganisms and so on. By previous pharmacological studies, they have been reported as an immune modulator to play a wide range of functional roles in anti-tumor, anti-virus, anti-infective, anti-oxidation and the regulation for blood glucose and lipids. On the basis of their low toxicity, more and more concerns have recently been paid to the correlative research with bioactive polysaccharides in the modern medicine and food industry field.In this study, we chose" Yu purple sweet potato 263" as our research objective, which harvested from Sun Town in Lin'an City of Zhejiang province. By use of biochemical purification, chemical structure analysis and animal model experiments and other means, we developed the studies of purple sweet potato from polysaccharide (PPSP) in its extraction, isolation and purification process, and experimental optimization of the conditions, and its role in regulating blood lipid and glucose in vivo, as well as antioxidant activity in vitro and in vivo. In summary, the main conclusions are drawn as follows:(1) The optimum extraction conditions of PPSP were studied by designing orthogonal experiment, and the following optimum conditions were known as: the ratio of the sample weight to the solvent volume is 1:15; the temperature is 70℃; 2 hours for extraction. In addition, the polysaccharide yield was shown to be influenced by two factors in the process of ethanol precipitation, the ideal conditions for precipitation were as follow: the ratio of sample weight to volume of concentrated solution is 1:2; the final concentration of ethanol is 85% and 3 times.(2) Four components were separated from PPSP with a single peak after eluted by DEAE-cellulose column chromatography under a combination of different concentrations and choosing with different kinds of elution buffers as follow: water, 0.05mol/L NaHCO₃ buffer,50mmol/L PBS buffer, 0-2mol/LNaCl and 0.5mol/LNaOH +1.5mol/LNaCl buffer and subsequently collected as PPSPâ… , PPSPâ…¡, PPSPâ…¢and PPSPâ…£after further dialysis desalting and desiccated under vacuum. The preliminary structural analysis was further made respectively for PPSPâ…¡and PPSPâ…¢.(3) The effects of PPSP on the metabolism of glucose and lipids in diabetic rat induced by streptozotocin (STZ) were studied in vivo as well as underlined mechanism. By observing the serum glucose, glycosylated serum protein (GSP), hepatic glycogen, total cholesterol (TC), triglyceride(TG) and high density lipoprotein cholesterol (HDL-C), the results indicate that PPSP could significantly increase the synthesis of hepatic glycogen, while it might decrease the content of serum glucose, GSP, TC and TG, which suggests that PPSP can significantly attenuate hyper -lipidemia and hyperglycemia in diabetic rat, probably due to the regulatory function of PPSP on the metabolism of hepatic glucogen and antioxidation.(4) PPSP was shown its significant antioxidant effect in vitro and in vivo. By establishing the reaction system of hydroxyl radical, DPPH free radical and reducing power, we detected antioxidant activity of PPSP with different doses in vitro. The contents of MDA, the activities of SOD, GSH and T-AOC in liver and pancreas were respectively measured in oxidative diabetes mellitus rat model caused by streptozotocin. In addition, we found that the contents of MDA were decreased and the activities of SOD, GSH and T-AOC were increased in both liver and pancreas Moreover, liver rescue was observed in the liver tissue obtained from STZ-inducing diabetic rat by middle dose PPSP extract taken.