Study On Hypoglycemic Activities And Chemical Constituents Of Two Medicinal Plants Of Anoectochilus Genus

Diabetes mellitus is a group of chronic metabolic disorders characterized by hyperglycemia.The number of diabetic patients has been increased rapidly;however,the control of diabetes without side effects remains to be a challenge.There is an increasing demand by patients to use the natural products with antidiabetic activity,due to obvious side effects associated with the use of insulin and oral hypoglycemic agents.The genera Anoectochilus(Orchidaceae)are perennial herbs which comprise more than 40 species and is widespread in the tropical regions.Of those species,Anoectochilus chapaensis,an indigenous and valuable Chinese folk medicine,has been used as a popular nutraceutical herb in China and other Asian countries.However,few report has been available about this herb’s constituents and activity.In this study,streptozotocin(STZ)induced hyperglycemia model on rats were employed to evaluate the hypoglycemic activity of different fractions from A.chapaensis.The total EtOH extract was suspended in distilled water and partitioned in sequence with petrol ether(PE),ethyl acetate(EtOAc),n-BuOH,thus yielding four fractions,all of which were orally administered to further investigate the biological activity and pharmacological mechanism that involves in the hypoglycemic effect in diabetic rat model induced by high lipid diet plus STZ.Our study showed that the EtOAc fraction from this plant exhibited the most significant antihyperglycemic activity,which may be partially attributed to modulating the activity of enzymatic anti-oxidants,sensitizing insulin activity,reducing the content of factor NO,and so on.Much more intact β cells in the islets of Langerhans with denser insulin in extracts-treated groups than the negative control were observed,which greatly supported the morphological and functional elucidation.These results displayed that the EtOAc fraction from A.chapaensis could be useful in repairing β cells in pancreatic islet injury as well as improving its function.The OGTT evidenced that this plant could promote the endurance capacity of acute glucose increase in diabetic rats.The effect of different fractions from A.chapaensis on blood lipid and renal function were also examined.Total cholesterol(TC),triglyceride(TG),low density lipoprotein cholesterol(LDL-C),and high density lipoprotein cholesterol(HDL-C),creatinine(CRE)and blood usea nitrogen(BUN)in rats’ plasma were assayed.Morphological examination of the kidneys were performed.On the whole,the EtOAc fraction from A.chapaensis showed the best profile in hypoglycemic effect,improving hyperlipidemic indexes and renal functions.The EtOAc fraction from A.chapaensis may be the active part of reducing blood lipid and improving renal function.Because of a low budding and growth rate in natural surroundings,predatory mass collection,and damages to the ecological environment,the natural resources of A.chapaensis are becoming exhausted.The effect of other three different extracts from Anoectiochilus on blood glucose,lipid and renal function were investigated in high lipid diet plus STZ induced diabetic rats.The total EtOH extracts were prepared from A.lanceolatus,A.moulmeinensis and A.elwesii,thus yielding three extracts.On the whole,the total extract from A.elwesii showed the best profile in reducing blood glucose,improving hyperlipidemic indexes and renal functions.30 constituents from whole herbs of A.chapaensis were isolated and purified by repeated column chromatographies with silica gel,sephadex LH-20 and pre.TLC,etc.Of them,25 structures were elucidated by their physical and spectral data,comprising of 5 tritepenes,4 flavones,5 phenolic acids,1 dihydrophenanthraquinone,4 sterols and 6 aliphatic derivatives.8 compounds,including epifriedelanol,5a,8a-epidioxyergost-22-en-3β-ol,octadecanoic acid,dibutyl phthalate,friedelane,octacosanoic acid octadecanyl ester,2a,3β-dihydroxyolean-12-en-23,28,30-trioic acid,caffeic acid and 7-hydroxy-2-methoxy-9,10-dihydrophenanthrene-1,4-dione were isolated from genera Anoectochilus for the first time and all compounds were isolated from this species for the first time.16 compounds were obtained from A.elwesii by repeated column chromatographies over silica gel,sephadex LH-20 and recrystalization.By physical-chemical properties and spectroscopic data,14 compounds were identified,comprising of 10 compound which were the same as A.chapaensis,and the 4 different ones were as follows:myristic acid,ursolic acid,3-β-O-olean-11,13(18)-diene-23,28-dioic acid,and isorhamnetin-3-O-β-D-glucopyranosyl(1->2)-a-L-rhamnopyranosyl(1 →6)-β-D-glucopyranoside.3-β-O-olean-11,13(18)-diene-23,28-dioic acid and isorhamnetin-3-O-β-D-glucopyranosyl(1→2)-α-L-rhamnopyranosyl(1→6)-β-D-glucopyranoside were new compounds.All of the compounds were isolated from this plant for the first time.The inhibiting effect of 10 samples from the genus Anoctochilus on recombined PTP1B in vitro were investigated,and all of them showed good pharmacological profile as follows:isorhamnetin,isorhamnetin-3-O-β-D-glucopyroside,isorhamnetin-3-O-β-D-rutinoside,sorghumol,friedelin,friedelane,epifriedelanol,2a,3β-dihydroxyolean-12-en-23,28,30-trioic acid,5α,8a-epidioxyergost-22-en-3β-ol and sterols.These compounds may be considered to be good potential candidates,and their acitivity in vivo deserves deep research.Chemical constituents and pharmacological activity of the medicinal plants of the genus Anoectochilus were investigated in this study.2 novel compounds were ilucidated,and the distribution of the main constituents in A.chapaensis and A.elwesii were illuminated,which may provide scientific foundation for the discovery of lead compounds and quality evaluation of the medicinal plants.