| Dendrobium nobile Lindl.,derived from the dried or fresh stems of several Dendrobium species(Orchidaceae),is widely distributed in the south of the Yangtze River,such as Guizhou and Yunnan.D.nobile is one of the traditional precious herbs in China and has the usage of nourishing yin and clearing heat,strengthening the spleen and stomach,and relieving cough and so on.At the same time,it is proved by the modern pharmacological experiments that D.nobile has obvious effect on enhancing human immunity,anti-oxidation blood sugar lowering,inhibiting the growth of tumor cells and anti-aging,therefore,it has widely attracted extensive attention from scholars around the world.Its mainly medicinal chemical components are alkaloids,sesquiterpenoids,bibenzyls,phenanthrenes and polysaccharides.In this study,the chemical constituents and biological activities of this plant were studied,in order to excavate more biologically active compounds,which provided a basis for the development and utilization of the gangue resources.In this paper,nineteen compounds were isolated and identified from the ethanol extract of the stem of D.nobile by the method of column chromatography and high performance liquid chromatography.On the basis of spectral data and physical and chemical properties,their structures were identified as dendroterpene A(1),dendroterpene B(2),dendroterpene C(3),dendroterpene D(4),dendroterpene E(5),nobilin E(6),dendrocandin V(7),(6S,7E)-6-hydroxy-4,7-megastigmadien-3,9-dione(8),di-[2-(4-hydroxyphenyl)]ethyl ether(9),methyl p-hydroxyphenylacrylate(10),salicylis acid(11),p-hydroxy-benzaldehyde(12),vanillin(13),3,4-dihydroxy benzoic acid(14),cinnamic acid(15),(E)-4-(4-Hydroxy-3-methoxyphenyl)but-3-en-2-one(16),phthalic acid diisobutyl ester(17),dibutyl phthalate(18)and bis(2-ethylhexyl)benzene-1,2-dicarboxylate(19).Among them,compounds 1-5 are new sesquiterpenoids,compounds 9,10 and 16 are isolated from this genus for the first time,and compound 8 is isolated from D.nobile for the first time.The cytotoxic activities(human hepatoma cells BEL-7402,lung cancer cells A549,chronic myelogenous leukemia cell line K562,gastric carcinoma cell SGC-7901 and cervical cancer cell Hela)of compounds 1,3-16 were measured in vitro by MTT method.The results showed that compound 6 has significant cytotoxic activities against those tumor cells,and IC50 values were 17.30±0.06、10.39±0.03、29.03±0.07、20.13±0.07 and 22.19±0.03 μM.Compound 7 had a cytotoxic effect on human chronic myeloid leukemia cell line K562,and the IC50 value was 28.23±0.05μM,and had a weak inhibitory effect on the proliferation of human gastric cancer cell line SGC-7901 and the IC50 value was 43.10±0.03μM,respectively.Compounds 1 and 3-16 were tested for a-glucosidase inhibitory activity by the optimized PNPG method.The results showed that compounds 1,3,6,7,9,10,11,12 and 15 presented strong inhibitory activity against a-glucosidase,and the inhibition rate is between 65 and 100%. |
