| “Baimaigashai”is the flags and leaves of Draconian Indochinese,commonly called as dragon blood leaves.Dragon blood leaves can be used to treat diabetes according to theDai "Bayeux" and the folk feedback.However,there are some questions unclear about the hypoglycemic effect of the dragon blood leaves: the mechanism of action is unclear,the functional factors are unknown,and the quality standard is not standardized,which prevent the process of development of dragon blood leaves to the diabetes health foods or clinical drugs.In order to solve these problems,this dissertation mainly carries on the following research contents.First,the acute toxicity of the water extract of dragon blood leaves was studied.The result showed that the maximum tolerated dose of the water-extract drgadon blood leaves was more than 20 g/kg in acute oral toxicity test of female and maleICR mice.According to the acute toxicity grading standards in "Health food inspection and evaluation of technical specifications"(2003 edition),the water-extract drgadon blood leaves is non-toxic.An important way to treat diabetes is to inhibit the activity of ?-glucosidase in the small intestine by competitive inhibition,so that the rate of glucose absorption in the intestinal tract slows down,thus effectively controlling or alleviating the symptoms of rapid blood glucose rise after eating.Consequently,under the guidance of ?-glucosidase inhibitory activity,the active components of ?-glucosidase inhibitory activity from the dragon blood leaves were explored by the modern extraction and separation technique.The results showed that the fraction of ethyl acetate eluted by80% methanol / water in macroporous resin was the most efficient component,the inhibitory rate of ?-glucosidase of which was 55.7% and 78.8% at 1250 mg / L and2500 mg / L,respectively.And they showed the similar activity with positivity acarbose at the same concentration.Subsequently,we isolated thirteen compounds from the ?-glucosidase inhibitory active of the dragon blood leaves by means of a modern chromatographic technique,and they were identified by means of 1D-NMR and MS techniques.They are2'-hydroxy-5-methoxycinnamic acid(1),2'-methoxy-4',4-dihydroxychalcone(2),3-hydroxy-4-methoxybenzoic acid(3),4',7-dihydroxy-dihydroisoflavone(4),7,4'-dihydroxy-8-methoxy dihydro(5),4,4'-dihydroxy-2-methoxy dihydrochalcone(6),7,3'-dihydroxy-4'-methoxyflutane(7),7,4'-dihydroxy-3'-methoxyflutane(8),loureirin A(9),4,4'-dihydroxy-2,6-dimethoxy dihydrochalcone(10),diosgenin(11),7,4'-dihydroxy dihydroflavone(12),and(2E)-3-(3,4-Dihydroxyphenyl)-1-(2,4-dimethoxyphenyl)-2-propen-1-one(13).At last,the above compounds were tested for ?-glucosidase inhibitory activity,and the results showed that compounds 2,6,12 and 13 had strong inhibitory activity,and theirIC50 were 60.5,90.7,9.5 and 62.5mg / L,respectively.In order to explore the presence of active substances with improvement of insulin sensitivity in the leaves of the dragon blood,the insulin resistance model of HepG-2 cells was successfully established in this study and the fractions of the dragon blood leaves extracts were screened.Compared with HepG2 insulin resistance group,treatment with 100 mg /L of the ethyl acetate fraction and n-butanol fraction of dragon blood leaves could alleviate insulin resistant HepG2 cells significantly.Based on the fact that the flavonoids have good insulin resistance activity,six flavonoids isolated from dragon blood leaves in Chapter 3 were treated on insulin-resistant HepG2 cells for 24 h at concentrations(2,5,and 10 ?M)to investigate the effects on glucose uptake.The results showed that compound 2(5?M)couldinduce the greatest increase in glucose uptake followed by compound4(10?M).In the final part of thedissertation,we reviewed the progress of screening hypoglycemic flavonoids using hypoglycemic in vitro screening models such as?-glucosidase inhibitory activity,HepG2 cell model and 3T3-L1 cell model.This review provides a theoretical reference for the follow-up work. |
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