Study On Anti-diabetic Activity Of The Vaccinium Bracteatum Thunb. Leaves Polysaccharides

Vaccinium Bracteatum Thunb.(VBT) is a resource of traditional Chinese herbs, whichleaves (VBTL) had been used as medicine or food for a long time in China. In this paper, thepolysaccharide was extracted from VBTL and the effects of VBTL polysaccharide (VBTLP)on type2diabetic mice were investigated.Based on the response surface method, the optimal extraction process was established asfollows: pH was9.5, temperature was65°C, duration was2.5hour, and the ratio betweenmaterial and water was1:45(m:V). By this method,68.63mg crude polysaccharide could beextracted from1g VBTL, and the purity of VBTLP was38.27%. The purity of VBTLP wasincreased to52.03%by treated as the following method: the alcohol precipitation static timewas6h, the volume ratio between extracting agent and alcohol was1:5, the ethanolconcentration (V:V) was95%. The purity of VBTLP was enhanced to76.69%by treated withresin.The anti-diabetic activity of VBTLP in streptozotocin-induced diabetic mice wasinvestigated. Mice were divided into5groups: NC (non-diabetic control mice group), MC(model control of diabetic mice, received isotonic saline solution), PC (positive control ofdiabetic mice, received500mg/kg body weight of dimethylbiguanide), LDG (low dose groupof diabetic mice, received60mg/kg body weight of VBTLP), and HDG (high dose group ofdiabetic mice, received180mg/kg body weight of VBTLP). After administration of VBTLPfor6weeks, the blood glucose (BG) levels of LDG and HDG were reduced to75.7%and65.2%, respectively, which were significant lower than that of MC. VBTLP showed adose-dependent decrease the BG level, and the time effect of VBTLP on BG level was alsosignificant. The insulin level of HDG were obviously higher (p<0.05) than that of MC.Comparing with MC, HDG and LDG had significantly lower (p<0.05) TC or LDL-cholesterollevels and similar TG or HDL-cholesterol levels. In comparison with NC, HDG and LDG hadsimilar plasma lipid levels except higher LDL-cholesterol level. Although the body weights ofLDG and HDG were significant lower (p<0.05) than that of the NC from week2to week6,they were similar to that of PC. The pancreatic beta cell function and insulin secretion indexwas1.83times and1.64times to those of MC. As compared to MC, the antioxidant capacityof mouse’s liver was significantly enhanced. The SOD, CAT and GSH-Px activity wereincreased2.49%,1.74%and6.04%, respectively, while the MDA content reduced to6.12%(p<0.05). It seemed the beta cell was repaired by high level of VBTLP, because the structures ofbeta cells of HDG were more similar to those of NC than LDG. Based on all the results, wespeculsted the anti-diabetic activity of VBTLP in STZ-induced diabetic mice resulted fromstimulating insulin secretion, reparing the beta cell, or enhancing the antioxidant capacity.The antioxidant activity of VBTLP in vitro was also estimated. The results showed that0.1mg/mL of VBTLP clear DPPH, hydroxyl radicals, lipid peroxidation inhibition rate andmetal chelating rate were40%,80%,40%,93%.