Chemical Constituents From Three Medicinal Plants And Their Bioactivities

The chemical constituents from three medicinal plants,Xanthium sibiricum Patr.,Clematis armandii Franch,and Cratoxylum formosum subsp.pruniflorum,have been chemically reinvestigated.In total,fifty-six naturally occurring compounds were obtained by using column chromatography(CC)over silica gel,MCI gel,Sephadex LH-20,and semi-preparative HPLC.The structures of fifty-three compounds were identified on the basis of extensive spectroscopic methods(IR,LR/HR EI-MS,1D/2D NMR)and a few chemical transformations,and six of which are new.Some bioactivities of the isolated compounds have been evaluated.The main research topics in this thesis are outlined as follows:1.The EtOH extract of the aerial parts of X.sibiricum afforded fourteen compounds,including six sesquiterpenes(1-6),four steroids(8-11),one triterpene(12),one megastigmane glucoside(13)and two sulfur-containing compounds(7,14).The structures of the new eremophilanolides(1,2)were established on the basis of spectroscopic methods and the modified Mosher's method to be the C-11 epimers of 2S,4S,5R,7R,8R-2-hydroxy-eremophil-1(10)-en-12,8-olide[11R:1(sibiriolide C);11S:2(sibiriolide D)].The isolated compounds were evaluated for their in vitro cytotoxicities against five human cancer cell lines(Huh-7 hepatocarcinoma,KB nasopharynx carcinoma,Jurkat T cell lymphoblast,BGC-823 and KE-97 gastric carcinoma)using the CellTiter-GloTM luminescent cell viability assay method.Compounds 4-6,each possessing an ?-methylene-?-lactone moiety,were found to have noteworthy cytotoxic effects with IC50 values ranging from 1.1 to 18.0 ?M.2.Twenty-three compounds,including seventeen lignanoids or phenylpropanoids(15-31),one steroid(32),one triterpenoid(33),a chromone(34),one coumarin(35)and two aromatic aldehydes(36,37),were isolated from the CH2Cl2 fraction of the ethanol extract of C.armandii.By application of spectroscopic methods,the structures of the new lignanoids(15,17)were established as(-)-trans-9-acetyl-dehydrodiconiferyl alcohol(armannan A)and(+)-erythro-2,3-bis-(4-hydroxy-3-methoxyphenyl)-3-methoxy-propanol(armannan B),respectively.The isolated compounds 15-37 were evaluated for their anti-inflammation activtities.Neolignans 15 and 16 were found to significantly inhibit the NO production in both BV-2 and RAW 264.7 cells.3.From the ethanol extract of the leaves of C.formosum subsp.pruniflorum,sixteen compounds were characterized,including two flavanone derivatives(52,53).four xanthones(38-41),two flavonols(42,43),five quinonoids(44-48),two pentacyclic triterpenoids(49,50),and one sesquiterpenoid(51).Among them,formones A(52)and B(53)were new compounds.The absolute configuration of 52 was established by X-ray diffraction and CD experiments.Additionally,the known compounds 43,46-48 were obtained from this plant for the first time.Cytotocities,anti-inflammation and neuroprotective activities of the isolates 38-53 were evaluated.Two xanthones(38,39)and four anthraquinoids(44-46,48)were found to have noteworthy cytotoxic effects against U-20S and A-549 cancer cells,with IC50 values ranging from 2.1 to 12.3 ?M.Besides,compounds 41 and 42 showed remarkable neuroprotective effects against A?25-35 induced cell injury at 1 or 10 ?M(the protective effect>10%).Moreover,compounds 38,41 and 42 were found to significantly inhibit the NO production in BV-2 cells,indicative of their potential anti-inflammation and anti-aging activities.