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Structures of three new sesquiterpene lactones 1-3, isolated from the pericarps of Illicium merrillianum, have been assigned as 14-O-benzoylfloridanolide, 2,10-epoxy-3-dehydroxypseudoanisatin and 7-O-methylpseudomajucin on the basis of spectroscopic data and chemical transformation. The structure of 2, having an ether linkage between C-2 and C-10, has been confirmed by X-ray crystallographic analysis.
The stereo structure of piperidine lactone (3), an intermediate of the antimalarial agent febrifugine ((+)-1) prepared by a synthetic method, was re-revised to the cis-form from the trans-form.
Bioassay-directed fractionation of an ethanolic extract of stems of Vernonia cinerea has resulted in the isolation of two novel sesquiterpene lactones, vernolide-A and -B. Their structures were elucidated on the basis of spectroscopic analysis. Biological evaluation showed that vernolide-A demonstrated potent cytotoxicity against human KB, DLD-1, NCI-661, and Hela tumor cell lines (ED(50)=0.02, 0.05, 0.53, 0.04 microg/ml for KB, DLD-1, NCI-661, and Hela, respectively); vernolide-B had marginal cytoxicity (ED(50)=3.78, 5.88, 6.42 microg/ml for KB, NCI-661, and Hela, respectively).
A new sesquiterpene lactone, 5-isopropyl-3-methyl-2,4,7-trimethoxy-8,1-naphthalene carbolactone (1) together with a known naphthoquinone, 8-formyl-7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthoquinone (2) were isolated from the root bark of Bombax malabaricum. The structures of these two compounds were established by extensive one- and two-dimensional (1D- and 2D)-NMR spectral studies.
Two new lactones (1, 2), descurainolide A and B, and one new aryl-8-oxa-bicyclo[3,2,1]-oct-3-en-2-one (3), descurainin, together with five known compounds (4-8), were isolated from the seeds of Descurainia sophia (L.) WEBB ex PRANTL. The structures of the new compounds were elucidated by extensive studies of their 1D, 2D NMR and HR-MS. Compounds 4 and 5 showed cytotoxicity.
Phytochemical investigation of Ixeris chinensis NAKAI (Asteraceae) has resulted in the isolation of a new guaianolide-type sesquiterpene lactone, ixerochinolide (1) as well as the related glucoside, ixerochinoside (2). In addition, the known guaianolides, 8beta-hydroxy-3-oxo-guaia-4(15),10(14),11(13)-trien-1alpha,5alpha,6beta,7alphaH-12,6-olide (8beta-hydroxydehydrozaluzanin), 8beta,15-dihydroxy-2-oxo-guaia-1(10),3,11(13)-trien-5alpha,6beta,7alphaH-12,6-olide (lactucin), 3beta,8alpha,10alpha-trihydroxy-guaia-4(15),11(13)-dien-1alpha,5alpha,6beta,7alphaH-12,6-olide (10alpha-hydroxy-10,14-dihydro-desacylcynaropicrin) and 3beta-D-glucopyranosyloxy-8beta-(p-hydroxyphenylacetyloxy)-guaia-4(15),10(14),11(13)-trien-1alpha,5alpha,6beta,7alphaH-12,6-olide (8-epicrepioside) were identified. The structures were determined on the basis of spectral analyses, especially 1- and 2D NMR. Compound 1 exhibited significant cytotoxicity against human PC-3 tumor cells.
Two new sesquiterpene lactones with the unusual sulfonic acid group, 13-sulfo-dihydrosantamarine (1) and 13-sulfo-dihydroreynosin (2), have been isolated from the roots of Saussurea lappa C. Their structures, including the absolute configurations, were elucidated by spectroscopic methods.
As a part of our ongoing interest in new bioactive compounds from natural sources, we studied Laurus nobilis (Lauraceae). This plant is widespread in the Mediterranean area and is used for medicinal and economic purposes. Chromatographic separations on active extracts led to the isolation of two new sesquiterpene lactones, 5a,9-dimethyl-3-methylene-3,3a,4,5,5a,6,7,8-octahydro-1-oxacyclopenta[c]azulen-2-one (1) and 3beta-chlorodehydrocostuslactone (2). The structures of the new compounds were identified by 1D and 2D NMR experiments, as well as high resolution mass spectrometry. The cytotoxic activity was also evaluated against three different tumor cell lines of human origin.
Two new sesquiterpene lactones, spicatolide C (1) and spicatocadinanolide A (2), have been isolated along with the known piptocarphol isomers (3, 4) and one eudismane type sesquiterpene (5) from the EtOAc extract of the aerial parts of Pseudoelephantopus spicatus. The structures and the relative stereochemistries of the new metabolites were determined by spectroscopic methods.
When 17 macrocyclic lactone antibiotics were examined for their abilities to inhibit gastric H+,K(+)-ATPase, copiamycin A was found to have the strongest and relatively specific activity with IC50s of 15.7 micrograms/ml and greater than 100 micrograms/ml against the hog gastric H+,K(+)-ATPase and the dog kidney Na+,K(+)-ATPase, respectively. Furthermore, this antibiotic inhibited the histamine-induced gastric acid secretion in the isolated gastric mucosal membrane of guinea pigs and the gastric ulcer formation in pylorus-ligated rats.
Six main sesquiterpene lactones (germacranolides) from Calea urticifolia were evaluated for in vitro cytotoxicity against human tumor cell lines HL60 and SW480 cells. Among them, arucanolide and parthenolide displayed marked cytotoxicity against both cell lines. Arucanolide exhibited a low IC(50) in HL60 cells. The cytotoxic activity of arucanolide was observed at lower concentrations compared to that of parthenolide, which has been reported to be a typical and simple germacranolide. The activity was found to be mainly due to apoptosis that was assessed by morphological findings, DNA ladder formation (24 - 36 h), and flow cytometric analysis in HL60 cells. Western blotting and an apoptosis inhibition assay using caspase inhibitors did not demonstrate the activation of any caspases tested. However, the mitochondrial membrane potential of HL60 cells was lost after 24-h treatment with arucanolide, and concurrently apoptosis-inducing factor (AIF) released from mitochondria was detected by Western blot analysis. The inactivation of nuclear factor-kappaB, which has been commonly shown in parthenolide-induced apoptosis, did not occur in arucanolide-induced apoptosis. Taken together, the findings presented here indicate that arucanolide induced marked apoptosis in HL60 cells mainly by dissipating mitochondrial membrane potential, which would trigger AIF-induced apoptosis.
The tumor promoter (-)-indolactam-V (1) exists in two stable conformers (twist and sofa) due to isomerization of the amide group. Indolactone-V (2), the lactone analogue of 1, has been synthesized to investigate the effects of the amide group on its conformation and biological activities. Indolactone-V (2) existed only as the inactive sofa-like conformer, indicating that the amide group of 1 plays a critical role in formation of the active twist conformation.
The oviposition response of the Rutaceae-feeding swallowtail butterfly, Papilio bianor, was induced by a methanolic extract from leaves of its major host, Orixa japonica. Several components were responsible for this oviposition response. One of the stimulants was isolated and identified as (-)-2-C-methyl-D-erythrono-1,4-lactone. The compound was inactive alone, but elicited oviposition behavior when mixed with other fractions.
5-Oxa-7-epi-jasmonic acid and 5-oxa-jasmonic acid, which are stereochemically restricted lactone-type analogues of jasmonic acids, were synthesized via three-component coupling of 2(5H)-furanone, tert-butyl acetate and 1-bromo-2-pentyne. After acidic deprotection of the tert-butyl esters, the (Z)-olefin was introduced by catalytic partial reduction with the Lindlar catalyst to give the desired analogues.
The glucosidic precursor of marmelo lactones was synthesized by employing a common intermediate which had been used for the synthesis of the glucosidic precursor of marmelo oxides. The synthesis was performed by modifying the former procedure. Monochloroacetyl was adopted to protect both the glucose and aglycon hydroxyl groups for selective transesterification in the presence of the glycosyl ester. Glycosylation of the aglycon carboxyl group with 1-alpha-bromopermonochloroacetylglucose and final selective alcoholysis yielded the target glucoside.
Acremolactone A was chemically degraded to the bicyclic hemiacetal gamma-lactone and an epoxycyclohexenol, and their stereochemistry was determined by spectroscopic methods. These observations and data from NOE experiments on acremolactone A led to the configurational assignment of all asymmetric carbons in acremolactone A, enabling its stereostructure to be established.
Aerial parts of Inula montana were investigated for its sesquiterpenoid composition. Five sesquiterpene lactones, isoinuviscolide, gaillardin, 1beta-hydroxy-3beta-acetoxy-eudesm-4(15), 11(13)-dien-12-8beta-olide, pulchellin-C and pulchellin-E were identified for the first time in this plant. One of them, 1beta-hydroxy-3beta-acetoxy-eudesm-4(15),11(13)-dien-1 2-8beta-olide, is a novel natural product. The structures of this compounds were established by 1D and 2D-NMR spectroscopy.
Aerial parts of Achillea collina afforded, in addition to five known sesquiterpene lactones two new germacranolides and one new eudesmanolide, the structures of which were elucidated by spectroscopic methods.