Extraction, Analysis And Hypoglycemic Activity Of Polysaccharides From Psidium Guajava Linn

Psidium guajava Linn (guava) was effective in prevention against diabetes but which component is responsible for it is still unknown. In this thesis, the extraction, isolation, purification, gradation, purity determination, and structure analysis of polysaccharides from pearl guava were extensively studied and their hypoglycemic effect in rats was investigated.Guava polysaccharides were extracted by hot water and precipitated by ethanol. The optimal extraction technology was obtained by single factor and orthogonal tests: one volume of homogenized slurry was mixed one volume of water and extracted at 80℃ for 2 hours. The extracts concentrates with 14% solid content were precipitated by ethanol with 80% final concentration, proteins in polysaccharides removed by Sevag method.The extracts were loeided upwards in a DEAE-cellulose column and three parts (part I -partIII) were obtained by washing out with water, 0.5mol/L sodium acetate, and 0.5 mol/L NaOH respectively. Part I was loaded upwards in a Seohacryl s-200 column and two constituents were eluted by their molecular size, namely P I a and P I b respectively. Part II and part III were separated by Seohacryl s-200 and polysaccharide II (P II) and polysaccharide III(P III) were obtained. Cellulose acetate electrophoresis and polyacarylamide gel electrophoresis proved that P I a and P II are homogenous polysaccharides with high purity.Ion-chromatography detection indicated that P II was composed of D-pectinose, D-galactose, D-rhamnose, D-glucose, D-fructose and D-xylose, and the main component is D-pectinose. P I a was composed of D- pectinose, D-galactose, D- xylose and D-glucose.Alloxan-induced diabetes mellitus rats were used to test the hypoglycemic effect of guava polysaccharides on blood glucose. The results demonstrated that guava polysaccharides could reduce hyperglycemia, increase SOD activity in serum, and lower the MDA level in liver. Moreover, the polysaccharides also enhance the physical antioxidant capacity and improve growth of diabetic rats. Their hypoglycemic mechanism was also discussed...