Studies On The Chemical Constituents Of The Aerial Parts Of Dioscorea Opposite And Their ?-glucosidase Inhibitory Activities

Background Dioscorea opposita Thunb.(Dioscoreaceae)is one of the famous traditional Chinese Medicines which can be used both for food and medicine.The rhizome of D.opposite,called Shanyao,is distributes all over the world.Dioscotea Rhizo,ma has been widely used for treating diabetes for thousands of years in clinic.Many pharmacological studies showed that the extract and polysaccharide of Dioscotea Rhizoma had hypoglycemic activity.Recently,the chemical constituents and composition-groups of Dioscotea Rhizoma were found to possess the a-glucosidase inhibitory activities.The aerial parts of D.opposita are often discarded as waste when the rhizome of D.opposita is matured and harvested.This caused not only the waste of resources,but also the environmental pollution.So far,the studies on the aerial parts of D.opposita are very rare,and the hypoglycemic activity of the aerial parts of D.opposita has been not found.In order to reasonably develop and utilize the traditional Chinese medicine resources,the studies on the chemical constituents of the aerial parts of D.opposite and their a-glucosidase inhibitory activities were carried out.These researches will provide a scientific basis for the reasonable exploitation and utilization of Dioscotea Rhizoma.Objective(1)To investigate the chemical constituents from the aerial parts of D.opposita;(2)To screen the composition-groups and compounds with a-glucosidase inhibitory activity.Method(1)Compounds were isolated and purified by various column chromatographic methods including silica gel,Sephadex LH-20,ODS column chromatographies and Semi-HPLC.Their structures were elucidated on the basis of spectral analysis(1H-NMR,13C-NMR,MS)and physicochemical methods.(2)Composition-groups and compounds were screened by ?-Glucosidase Activity Assay Kit.Results(1)Thirty-three compounds were isolated from the aerial parts of D.opposita,including five phenanthrenes and its derivatives:7-hydroxy-2,6-dimethoxy-1,4-phenanthr-enedione(1),6,7-dihydroxy-2-methoxy-1,4-phenanthrenedione(2),volucrin(3),6-hydr-oxy-2,4,7-trimethoxyphenanthrene(4),7-hydroxy-2,4,6-trimethoxyphenanthrene(5);six flavonoids:5,7,3',4'-tetrahydroxy-8-C-?-D-glucopyranosyl flavone(6),6-trans-[2"-O-(?-rhamnopyranosyl)]-ethenyl-5,7,4'-trihydroxyflavone(7),chrysoeriol(8),kaempferol-3-methylether(9),luteolin(10),quercetin(11);seven terpenoids:(S)-dehydrovomifoliol(12),blumenol A(13),(3R)-4-[(2R,4S)-2-hydroxy-2,6,6-trimethylcyclohexylidene]-3-buten-2-oneiol(14),pubinernoid A(15),9,19-cyclolart-25-en-3?,24R-diol(16),cycloeucalenol(17),epifriedelanol(18);two alkaloids:indole-3-carboxaldehyde(19),allantoin(20);one lignan:(+)-syringaresinol(21);one glucoside:n-Butyl-?-D-fructopyranoside(22),five sterols:(24S)-24-ethylcholsta-3?,5?,6?-triol(23),stigmast-4-en-3?,6?-diol(24),(3?,7?)-7-methoxystigmast-5-en-3-ol(25),(22E)-5?,8?-epidioxyergosta-6,22-dien-3?-ol(26),?-sitosterol(27);six others:p-hydroxybenzaldehyde(28),3,4-dihydroxybenzaldehyde(29),4-hydroxy-3-methoxybenzaldehyde(30),hexadecanoic acid 2,3-dihydroxypropyl ester(31),tetracosanoic acid(32),palmitic acid(33),respectively.(2)Half inhibitory concentration(IC50)of the petroleum ether fraction,ethyl acetate fraction,n-butanol fraction and water fraction from the aerial parts of D.opposita are 1.54±0.094 mg/ml,0.065±0.0022 mg/ml,1.33±0.24 mg/ml,177.43±1.46 mg/ml.Half inhibitory concentration(IC50)of compounds 1?3,5?12,16,21 and 28 are 3.04±0.25 mM.0.49±0.034 mM?0.07±0.0031 mM?4.13±0.023 mM?15.24±0.68 mM?0.27±0.0027 mM?1.17±0.009 mM?1.53±0.059 mM?0.49±0.073 mM?0.09±0.0021 mM?42.72±1.57 mM?0.37±0.0062 mM?35.60±4.32 mM?92.69±4.40 mM,respectively;compounds 13?15,19?20,22,30 are more than 100 mM.Half inhibitory concentration(IC50)of Acarbose is 61.57±1.40 mM,that is 39.75±0.90 mg/ml.Conclusion(1)Thirty-three compounds were isolated from the aerial parts of D.opposita.Compounds 1,3,5?19,21?26,28?32 were isolated from this plant for the first time.(2)Compared with acarbose,the petroleum ether fraction,ethyl acetate fraction and n-butanol fraction from the aerial parts of D.opposita were markly active against ?-glucosidase,which suggested they were the main active fractions.(3)Compared with acarbose,compounds 1?3,5?12,16,21 showed the obvious ?-glucosidase inhibitory effect.However,other compounds had no significant effect on the inhibitory effect of?-glucosidase.