Herapeutic Effects Of Pterocarya Stenoptera Aqueous Extract On Type 2 Diabetic Rats And Screening Of Its Active Components

Objective:To study the sugar and lipid-decreasing effects as well as protective effects of liver and kidney of pterocarya stenoptera aqueous extract(PSAE).To screen the main hypoglycemic active sites of P.stenoptera(PS),further isolate the active site monomeric compound.Using ?-glucosidase inhibitory activity screening model in vitro,to preliminary study the hypoglycemic mechanism of PS.Method:(1)Type 2 diabetic rats model was established by intraperito-neal injection of STZ(30mg·kg-1)and high energy diet.After successfully modeling,these rats were randomly divided into four groups including model group(T2DM),metformin group(DMBG,300mg·kg-1),PSAE(drug dosage 5g·kg-1)and Cyclocarya Paliurus aqueous extract(CPAE,drug dosage 5g·kg-1).Rats were fed with normal food and water,which were used as control group(Control).There were 10 rats in each group,which adiministered by intragastric administration,separately.Once a day for 8 weeks.Glycosylated hemoglobin(Hb A1c),fasting plasma insulin(FINS),insulin resistance index(HOMA-IR),fasting blood glucose(FBG),oral glucose tolerance test(OGTT),total cholesterol(TC),triglyceride(TG),high density lipoprotein cholesterol(HDL-C),low density lipoprotein cholesterol(LDL-C),blood serum urea nitrogen(BUN),creatinine(CREA),alanine aminotransferase(ALT),and aspartate aminotransferase(AST)were determined.(2)Type 2 diabetic mouse model was established by intraperitoneal injection of STZ(30 mg·kg-1)and high energy diet.After successfully modeling,these animals were randomly divided into six groups including T2 DM group,DMBG group(300 mg·kg-1),aqueous extract of PS group(PSAE,drug dosage 3g·kg-1),ethyl acetate extract of PS group(PSEE,drug dosage 3 g·kg-1),n-butanol extract of PS group(PSBE,drug dosage 3 g·kg-1)and water extract of PS group(PSWE,drug dosage 3 g·kg-1).Mice were fed with normal food and water,which were used as Control group.Adiministered by intragastric administration,separately.Once a day for one months,each group of 7 mice was retained,FBG in each group were determined.(3)The content of total flavonoids in PSAE,PSEE,PSBE and PSWE was determined by uv-vis spectrophotometry.The chemical constituents were isolated and purified by D-101 macroporous adsorption resin,Sephadex LH-20,and recrystallization.The structure elucidation was based on physicochemical properties and spectroscopic methods.Established ?-glucosidase inhibitory activity screening model in vitro,to evaluate the ?-glucosidase inhibitory activity of each monomeric compound.Results:(1)Compared with Control group,the rats in the T2 DM group showed significantly higher levels of Hb A1 c,FINS,HOMA-IR,FBG,TC,TG,LDL-C,BUN,CREA,AST and ALT(P<0.01).(2)Compared with T2 DM group,the levels of Hb A1 c,FINS,HOMA-IR,FBG,TC,TG,LDL-C,BUN,CRE,AST,ALT in PSAE group were significantly decreased(P<0.01,P<0.05),There was no statistical difference between the PSAE group and the CPAE group.(3)The blood glucose values at each time points in the T2 DM rats were significantly higher than those in the Control group.And the area under the curve(AUC)was also increased significantly(P<0.01).Compared with the T2 DM group,the blood glucose level and the AUC of the PSAE group were decreased significantly(P<0.01,P<0.05),There was no statistical difference between the PSAE group and the CPAE group.(4)Compared with the Control group,FBG of the mouse in the T2 DM group was significantly increased(P<0.05).Compared with the T2 DM group,the PSAE group,PSEE group,PSBE group and PSWE group can significantly reduce the FBG(P<0.05),which the PSEE group has extremely significant difference(P<0.01).(5)With quercitrin as the standard,the contents of total flavonoids in the extraction sites of PS were determined by Na NO2-Al(NO3)3-Na OH Colorimetry.PSAE(6.08±0.82)%,PSEE(12.51±1.10)%,PSBE(3.74± 1.38)% and PSWE(3.92±2.06)%).(6)Using the ?-glucosidase inhibitory activity screening model in vitro to screen the inhibition rate of each site of PS(final concentration 1000ug·ml-1),results as follows: PSAE(57.98±6.37)%,PSEE(87.13 ±3.11)%,PSBE(35.9±6.51)% and PSWE(43.19±3.89)%,where the inhibition of ?-glucosidase at the PSEE was most pronounced,less than the positive drug acarbose(98.75±0.73)%.(7)Eleven compounds were isolated and identified from the PSEE,(1)?-glucoside,(2)salicylic acid,(3)quercitrin,(4)p-coumaric acid,(5)quercetin,(6)5-hydroxy-2-methoxy-1,4-naphthoquinone,(7)?-sito-sterol,(8)gallic acid,(9)kaempferol,(10)quercetin-3-O-?-D-galactopyra-noside;(11)protocatechuate;The compounds quercetin and kaempferol inhibiton rate of ?-glucosidase exceeds 90%.Conclusion:(1)PSAE showed sugar and lipid-decreasing effects on type 2 diabetic rats,and has the effect of improving liver and kidney function.(2)PSEE is the major hypoglycemic site of PS.And the active ingredient may be flavonoids.Inhibition of ?-glucosidase activity may be one of the mechanism of PS ruduce blood glucose.(3)Eleven compounds were isolated from the PSEE,of which compounds 2,3,4,9,10,11 were isolated from Pterocarya Kunth for the first time.