| Summary: | 碩士 === 高雄醫學大學 === 天然藥物研究所碩士班 === 93 === Dioscorea tuber has been used in medical treatment and functional food for thousand years. In this study, hypoglycemic activity was detected in polysaccharide-enriched fractions (PLE) and hot water extracts (HWE) of five kinds of Dioscorea tubers cultivated in Taiwan (numbers and origins: TA01: Dioscorea alata L., TA02: D. alata L., TA03: D. alata L. var. purpurea (Roxb.) M. Pouch., TA04: D. persimilis Prain et Burk. and TA05: D. alata L.) using streptozotocin (STZ) induced diabetic mouse/rat models. Animals showing blood glucose levels 250~300 mg/dL 48 h after STZ treatment were selected for study.
In STZ-diabetic mice model, treated with HWE of TA01, TA05, and PLE of TA01, TA02, TA05, respectively, for 14 days significantly (p<0.05) lowered the fasting blood glucose levels when compared with the STZ-diabetic mice group. According to the preliminary results, TA01 and TA05 showed the best hypoglycemic effect in those of five cultivated Dioscorea tubers. Furthermore, in STZ-diabetic rats model, glucose concentrations were increased in serum of diabetic animals in comparison to normal and were significantly improved after treatment with 300 mg/kg HWE of TA01、TA05 and 100 mg/kg PLE of TA01、TA05 p.o. for 7 days and 14 days (p＜0.001), respectively. In addition, all test drugs can reduce the productions of malondialdehyde (p＜0.01) and the ratio value of pancreas, kidney, liver weight to the body weight of rats (p＜0.05~p＜0.01). Otherwise, PLE of TA01 and TA05 showed the increasing of glycogen quantity in liver (p＜0.01~p＜0.001), and HWE of TA05 and PLE of TA01, TA05 increased insulin secretion in serum (p＜0.05~p＜0.01).
According to the results, the hypoglycemic effect of PLE is better than that of HWE in Dioscorea tuber. Furthermore, TA01 and TA05 showed the best hypoglycemic effect in those of five Dioscorea tubers cultivated in Taiwan. The mechanisms of the hypoglycemic effect on Dioscorea tubers in this study were considered to the ability of increased insulin secretion and then enhanced the bioconversion of glucose to glycogen in the liver. Moreover, decreased levels of lipid peroxidation in Dioscorea tuber indicative of organs protection in diabetic rats. Based on the result of this study, TA01 and TA05 are suggested to be developed as functional food for treatment of diabetes.
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