Study On The Hypoglycemic Constituents From Leaves Of Lagerstroemia Speciosa

Lagerstroemia speciosa L.(Lythraceae),a popular folk medicine known as "banaba" in Southeast Asia,originally distributes in tropical countries,such as India,Sri Lanka, Malaysia,Philippines and Vietnam.The roots are used as astringent in India,while in Malaysia,the leaves are used for the treatment of malaria and foot fracture.In Philippines, the leaves were processed into the tea for the treatment and prevention of diabetes mellitus. Without obvious side effect,it was called as "natural plant insulin".Recent years,it was cultivated in Southern China as ornamental plant.Many modern pharmacological researches have indicated that the leaves of Lagerstroemia speciosa abroad have the hypoglycemic activity.To authenticate the effect of civil cultivation and to investigate the active position,the green leaves(GL) and fallen leaves(FL) of Lagerstroemia speciosa that we collected from the Zhangzhou,Fujian Province,were applied in our research.The 80%ethanol percolate of leaves,was partitioned into five fractions as petroleum spirit(P1),dichloromethane(P2),acetic ether (P3),n-butanol(P4) and water fraction(P5).Guided by the documents,we establishedα-glucosidase andα-amylase reaction systems,which were used to investigate the enzyme inhibition activities of different extract.It was shown that both the GL and FL had the positive effect on theα-glucosidase andα-amylase reaction systems,with the inhibition rates of 29.06%and 30.49%for GL,and 25.42%and 13.96%for FL,respectively.P3 with the inhibition rate of 83.80%came to the most obvious activity inα-glucosidase,while P1 with the inhibition rate of 76.92%came to the most obvious activity inα-amylase.Besides, P2 had positive effect on both theα-glucosidase andα-amylase reaction systems,and P4 had positive effect on theα-glucosidase reaction system to some extent.(at 250μg/ml concentration of different extract)With the help of a variety of column chromatography methods,29 compounds were isolated from the leaves of Lagerstroemia speciosa.They were identified on the basis of spectral analysis(UV,IR,MS,¹H-NMR,¹³C-NMR and 2D-NMR) and phytochemical properties.10 compounds were obtained from P1,namelyβ-sitosteroi(Ls-1),ursolic acid (Ls-2),n-dotriacotanoi(Ls-3),daucosterol(Ls-4),asiatic acid(Ls-5),taraxasterol acetate (Ls-6),β-sitosterol acetate(Ls-7),2α-hydroxyuvaol(Ls-8),corosolic acid(Ls-9),alphitolic acid(Ls-10);9 compounds were obtained from P2,namely 3′,4′-di-O-methyl-3,4-methylenedioxy flavellagic acid(Ls-11),3,4,3′-tri-O-methyl flavellagic acid(Ls-12),3′-O-methyl-3,4-methylenedioxy ellagic acid(Ls-13),3,4, 3′,4′-tetra-O-methyl flavellagic acid(Ls-14),3,3′,4-tri-O-methyl ellagic acid(Ls-15),4,4′-di-O-methyl ellagic acid(Ls-16),campesterol(Ls-17),β-sitosterol-3-O-β-D-(6′-O-palmityi) glucopyranoside(Ls-18),caffeic acid ethyl ester (Ls-19);5 compounds were obtained from P3,namely kaempferol(Ls-20),quercetin (Ls-21),ethyl gallate(Ls-22),6,7-dihydroxy coumarin(Ls-23),caffeic acid(Ls-24);5 compounds were obtained from P4,namely 3,3′-di-O-methyl ellagic acid(Ls-25),3-O-methyl ellagic acid(Ls-26),ellagic acid(Ls-27),hyperin(Ls-28),(7S,8R)-dihydrodehydrodiconiferyl alcohol(Ls-29).Ls-5,Ls-8,Ls-11,Ls-12,Ls-13,Ls-14,Ls-19, Ls-20,Ls-21,Ls-22,Ls-23,Ls-24,Ls-28 and Ls-29 were isolated from Lagerstroemia speciosa for the first time.Four evaluation systems,including NF-κB activity detection system,α-glucosidase reaction system,α-amylase reaction system and NO releasing detection system,were established to investigate the mechanisms of hypoglycemic activity of Lagerstroemia speciosa.The results showed that Ls-2 had the most obvious activities in the NF-κB and NO inhibition while Ls-22 had the most obvious activities in theα-glucosidase andα-amylase inhibition.And Ls-22 showed good inhibition activities in all the evaluation systems mentioned above.It could be concluded that the different chemical constituents contained in the leaves of Lagerstroemia speciosa,might contribute to the hypoglycemic activity through different pathways.The primary pharmacokinetic study of Ls-22 in rat after oral ministration were investigated by high performance liquid chromatography coupling to mass spectrometry (LC-MS/MS) method successfully.Three metabolites of Ls-22 had been found through the rat blood analyses.One of them is ascertained to be gallic acid,and the other two products are still in further study.