Chemical Components And Bioactivities Of Dendrobium Sinense(Orchidaceae), An Endeimic Species In Hainan Island

The genus Dendrobium of family Orchidaceae has been used in traditional Chinese medicine as a Yin tonic to benefit the stomach, promote secretion and reduce fever. Previous chemical investigations on this genus have led to the isolation of a number of structurally interesting compounds such as stilbenoids, alkaloids and polysaccharides, some of which showed various bioactivities, such as cytotoxic, antioxidant and antibacterial activities. Dendrobium sinense T. Tang et F. T. Wang is a shrub endemic to Hainan province. To search for more bioactive constituents from the twigs of D. sinense, chemical constituents and bioactivities were studied under bioassay guidance for the purpose of developing this plant resource. The main results were as follows:1. Thirty-four compounds were isolated from the ethanol extract of the whole plant of D. sinense by column chromatography, and their structures were indentified by physicochemical properties and spectral data (UV, IR, MS, ID and2D-NMR) as denbinobin B (1), dendrosinen A (2), dendrosinen B (3), dendrosinen C (4), dendrosinen D (5), dendrosinen E (6),4,7-dihydroxy-2,3-dimethoxy-9,10-dihydrophenanthrene (7),4,7-dihydroxy-2,3,6-trimethoxy-9,10-dihydrophenanthrene (8),4,5-dihydroxy-2,3-dimethoxy-9,10-dihydrophenanthrene (9),5,4’-dihydroxy-3,4,3’-trimethoxybibenzyl (10), aloifol Ⅰ (11),3,4-dimethoxyl-5,3’-dihydr-oxy-ibibenzyl (12), longicornuol A (13), trigonopol A (14), coniferyl p-coumarate (15), sinapyl p-coumarate (16), syringaresinol (17), syringaresinol-4’-O-β-D-glucopyranoside (18),2-[4-(3-hydroxyl-l-propenyl)-2,6-dimethoxyphenoxyl]-3-hydroxy-3-(4-hydroxy-3,5-dimetho-xyphenyl)propyl-β-D-glucopyranoside (19), picraquassioside C (20), ursolic acid (21), methyl ursolate (22), matesaponin Ⅰ (23), kudinoside E (24), ilekudinoside O (25), ilekudinoside K (26), kudinoside C (27), conifery aldehyde (28), syringaldehyde (29),3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)-1-propanone (30),2-methoxy-4-(2-propen-1-yl)penyl-β-D-glucopyranoside (31), citronelly β-D-glucopyranoside (32), ectochrysin (33) and β-daucosterol (34) respectively. Among them, compound1was a new phenanthrenequinone, compounds2-5were new bibenzyls, compound6was a new lignans, and compounds7-34were isolated form D. sinense for the first time.2. All fractions and twenty phenolic compounds were examined for their antioxidant activities by DPPH and TEAC methods. The ehtyl actate frcation showed greatest DPPH and ABTS.+radical-scavenging acpacities; compounds3,5,10-14displayed potent antioxidant activities free radical scavenging capacities, all of which were equivalent to vitamin C or Trolox. The cytotoxicities of compounds1-34were evaluated in vitro using the MTT method. Compounds7,10-13showed cytotoxic activities towards chronic myelogenous leukemia (K562), human hepatoma human gastric (SGC-7901) and human hepatoma (BEL-7402). The antimicrobial activities against Staphylococcus aureus and Candid albicans of compounds1-34were measured using paper disco diffusion method, among them, compounds1,4,5,7,8,10-12,14,17,18,28and29exhibited antimicrobial activities in different degrees, and compounds7and12displayed inhibition against Candid albicans.