Sesquiterpene lactones from two newly-described species of Vernonia: V. jonesii and V. pooleae

Two novel, non-glaucofide, germacrolide sesquiterpene lactones, 8α-methacryloyloxycostunolide-1(10),4(5)-diepoxide and 1-oxo-10α-OH-8α-methacryloyloxycostunolide (not fully characterized), were isolated from Vernonia jonesii and the previously described glaucolide B was identified from V. pooleae. This is one of the few reports of non-glaucolide type germacrolides in a New World species of Vernonia, although members of this class of sesquiterpene lactones are common constituents of Old World species of the genus. The chemical evidence supports the suggestion that V. jonesii may be part of a relictual, isolated group of the New World Vernonia, closely related to some of the Old World taxa.     

11β,13-Dihydroguaianolides from Artemisia douglasiana and a thiophene acetylene from A. schmidtiana

The aerial parts of Artemisia douglasiana afforded, in addition to some known sesquiterpene lactones, 22 new closely related guaianolides. A new thiophene acetylene was isolated from the aerial parts of A. schmidtiana together with some known sesquiterpene lactones. The structures were elucidated by high field ¹H NMR spectroscopy.     

Allenic germacranolides,bourbonene derived lactones and other constituents from Vernonia species

An investigation of seven Vernonia species, mainly from northern Brazil, afforded in addition to known compounds three new unusual sesquiterpene lactones with an allenic group. Intensive NMR studies fully established the structures. Furthermore, two lactones derived from bourbonene, two new glaucolides, a new furansesquiterpene, a nerolidol derivative and two other sesquiterpenes derived from eudesmane were isolated. The biogenetic relationships of the sesquiterpene lactones present in Veronia species as well as the chemotaxonomic aspects are discussed.     

Anticancer sesquiterpene lactones of Michelia compressa (magnoliaceae)

Investigation of the cytotoxic active components of Michelia compressa afforded two new cytotoxic sesquiterpene lactones, michelenolide and micheliolide. Parthenolide, costunolide, santamarine, reynosin and liriodenine were also isolated and exhibited cytotoxic activity. The known sesquiterpene lactones, lanuginolide and dihydroparthenolide, were isolated but were not active. Two other new inactive sesquiterpene lactones, compressanolide and dihydroreynosin, were also obtained. The structures of michelenolide and micheliolide were confirmed by partial synthesis from parthenolide and the structure of compressanolide by partial synthesis from dihydroparthenolide.     

Glaucolides from Vernonia fulta

Four sesquiterpene lactones were isolated from the aerial parts of Vernonia fulta. Spectral characterization showed that three were new and one was known (i.e. glaucolide-B). The biogenetic relationship among these sesquiterpene lactones is discussed briefly.     

Pungent sesquiterpene lactones of the european liverworts Chiloscyphus polyanthus and Diplophyllum albicans

The characteristic pungency of the European liverwort, Chiloscyphus polyanthus, is due to a mixture of four sesquiterpene lactones, two new structures ent-5β-hydroxydiplophyllin and ent-3-oxodiplophyllin, and the previously known diplophyllin and diplophyllolide. A new dihydrodiplophyllin, together with the pungent diplophyllolide and diplophyllin, has been isolated from Diplophyllum albicans. Ent-dihydrodiplophyllolides derived from the above pungent diplophyllolides produce intense numbness of the tongue. All pungent sesquiterpene lactones showed inhibitory activity towards the germination and root elongation of rice husks.     

Confertdiolide,a novel sesquiterpenoid lactone from Parthenium

Four sesquiterpene lactones were isolated from several populations of Parthenium confertum var. lyratum (Gray) collected in Sierra de Arteaga, southern Coahuila. Three of the compounds, hysterin, tetraneurin E and hymenin were previously isolated from other Parthenium species. The fourth constituent is the new cyclopropanoid sesquiterpene dilactone confertdiolide which represents a new structural type. The photolytic conversion of hymenin into confertdiolide confirmed its structure.     

Cadinenes and other metabolites from Verbesina sphaerocephala A. Gray

The phytochemical study of the aerial parts of Verbesina sphaerocephala A. Gray afforded six sesquiterpene lactones of cadinene type, five of them described for the first time, along with known phenyl propanoids, terpenoids, and phenolic compounds. Structures on new compounds were elucidated by spectroscopic techniques including CD and X-ray analyses, and known compounds were identified by comparing their spectral data with those previously reported. Cadinene-like sesquiterpene lactones could be characteristic metabolites of V. sphaerocephala.     

Seven guaianolides from Eupatorium chinense

Two allyl hydroperoxy guaianolide sesquiterpene lactones (peroxyeupahakonin-A and -B) and five new guaianolides (eupahakonin-A and -B, eupahakonenin-A and -B, and eupahakonesin) were isolated from E. chinense and characterized. The allyl hydroperoxy sesquiterpene lactones were characterized by spectral and chemical methods. They were prepared chemically by photosensitized oxygenation of eupahakonin-A.     

Weitere isocedren-derivate aus Trixis paradoxa

The investigation of two further species from the tribe Mutisieae afforded in addition to known compounds three new sesquiterpene lactones and two further sesquiterpene esters, all closely related to compounds isolated before from other Trixis species. The isolation of these new substances from Trixis further establishes the chemotaxonomic situation in the subtribe Nassauviinae. From the Dinoseris species, among others, 1β-hydroxyalantolactone was isolated, indicating a relationship to the subtribe Gochnatiinae.     

Guaianolides from Ainsliaea fragrans

Five sesquiterpene lactones were isolated from Ainsliaea fragrans, two of them being new.     

Sesquiterpene lactones from Centaurea solstitialis

Eight sesquiterpene lactones were isolated from Centaurea solstitialis (yellow starthistle). They are solstitialin A, repin, subluteolide, acroptilin, janerin, cynaropicrin, and the new lactones solstitiolide and episolstitiolide.     

Sesquiterpene lactones from Michelia fuscata

Two new sesquiterpene lactones, desacetyllanuginolide and michefuscalide were isolated from Michelia fuscata along with two known lactones, dehydrolanuginolide, lipiferolide and a lignan, syringaresinol. The structures of desacetyllanuginolide and michefuscalide were determined by spectral and chemical methods.     

Sesquiterpene lactones from a further population of Artemisia herba alba

Two new sesquiterpene lactones, herbolides E and F, have been isolated from a further chemotype of Artemisia herba alba.     

Chemical constituents from Anthemis wiedemanniana Fisch. & Mey.

The lipophilic extract of the aerial parts of Anthemis wiedemanniana Fisch. & Mey, a Turkish endemic species, was investigated. In addition to one new natural product, namely 3,4,4-trimethyl-6-carboxy-cyclohex-2-ene-1-one, five known sesquiterpene lactones, five methylated flavonoids, one simple phenolic derivative and one nor-isoprenoid were isolated. Among the sesquiterpene lactones, canin was found to be the main compound.     

Eudesman-12,8β-olides and other terpenes from Artemisia species

The aerial parts of Artemisia iwayomogi afforded, in addition to already known terpenes, eleven new cudesmanolides whereas four new guaianolides were found in A. gmelinii. No sesquiterpene lactones were detected in the aerial parts of A. santolinifolia which afforded two new nerolidol derivatives besides several other already known compounds. From A. caerulescens var. cretacea six eudesmanolides were isolated, one of which has not been reported previously. The structures were elucidated by high field ¹H NMR spectroscopy and chemical transformations. The chemotaxonomic significance of sesquiterpene lactones within the section Abrotanum and the subgenus Seriphidium is briefly discussed.     

Subexpinnatin,a new guaianolide from Centaurea canariensis

Two sesquiterpene lactones, the new guaianolide subexpinnatin and aguerin B, were isolated from the aerial part of Centaurea canariensis.     

Germacranolides from Proteopsis Argentea

Proteopsis argentea (tribe Vernonieae) afforded in addition to known compounds three new sesquiterpene lactones, closely related to those isolated from Eremanthus species, indicating a close relationship between these genera.     

α-Humulene derivatives including a sesquiterpene acid with a rearranged carbon skeleton from Lychophorora columnaris

An investigation of Lychnophora columnaris afforded in addition to known compounds six new α-humulene derivatives and a rearranged sesquiterpene with a new carbon skeleton. These compounds and several sesquiterpene lactones isolated from this species seem to be of chemotaxonomic importance. The structures were elucidated by spectroscopic methods and a few chemical transformations including partial synthesis.     

Germacranolides from Eupatoriastrum nelsonii

The aerial parts of Eupatoriastrum nelsonii afforded, in addition to known sesquiterpene lactones, four new lactones all closely related to the germacranolides isolated previously from other genera of the tribe Eupatorieae. The structures were elucidated by spectroscopic methods. Chemotaxonomic aspects are discussed briefly.