Two sesquiterpene and three diterpene lactones from Acanthospermum australe

The aerial parts of Acanthospermum australe afforded two new sesquiterpene lactones, an acid and a cis,cis-germacranolide, as well as three diterpene lactones of a new type, most probably formed by intermolecular nucleophilic attack of the carboxyl group of an acid epoxide derived from geranylgeraniol. The structures were proposed on the basis of spectroscopic studies.     

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.     

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.     

Sesquiterpene lactones and systematics of the genus Artemisia

The sesquiterpene lactones isolated from species in the genus Artemisia have been reviewed in an attempt to better understand the phylogeny and systematics of the four sections (subgenera), Abrotanum, Absinthium, Dracunculus and Seriphidium, proposed by Besser in 1829. The absence of hair on the receptacle is the only morphological characteristic separating species of Abrotanum from the species of Absinthium. There are no chemical characteristics segregating the species in these two subgenera since both produce eudesmanolides and guaianolides that are identical or biosynthetically similar. This suggests that the two subgenera could be combined into one (Artemisia) as proposed by Poljakov. The subgenus Seriphidium is composed of two geographical groups, one in the Old World and the other in the New World. The Old World species almost exclusively produce sesquiterpene lactones in the eudesmanolide class whereas the New World species (section Tridentatae) produce eudesmanolides and guaianolides, many of the latter being identical or structurally related to the sesquiterpene lactones in New World Abrotanum species. The chemical data in conjunction with geographic distributions suggest that the subgenus Seriphidium is polyphyletic and that the section Tridentatae originated from Abrotanum. Consequently, the Tridentate should be recognized as a subgenus separate and distinct from the Old World Seriphidium. There was insufficient information from the subgenus Dracunculus for interpretation.     

Neue sesquiterpenlactone und thymol-derivate aus Inula-arten

The investigation of three Inula species affords, besides known compounds, two new sesquiterpene lactones and two new thymol derivatives. The chemotaxonomic situation in this genus is still very complicated.     

New germacrolide- and heliangolide-type sesquiterpene lactones from Melampodium linearilobum

Chemical analysis of Melampodium linearilobum yielded, besides coumarin, seven germacrolide-type sesquiterpene lactones, linearilobin A to G and two heliangolides, linearilobin H and I. All new sesquiterpene lactones are oxygenated at C-14 and C-15 and differ by the number and types of ester moieties at C-8, C-14 and C-15. M. linearilobum represents the first species within the genus known to produce germacrolides and heliangolides instead of the more common melampolides.     

Germacranolides,a guaianolide with a β-lactone ring and further constituents from Grazielia species

An investigation of three Grazielia species afforded, in addition to known compounds, several new sesquiterpene lactones, eight germacranolides, two melampolides and one guaianolide as well as three diterpenes, two geranylgeraniol derivatives and a labda-diene. Three of the sesquiterpene lactones had an additional β-lactone ring, one an acid function, and two others unusual ester functions. The structures were elucidated by spectroscopic methods and some chemical transformations. The chemotaxonomic situation is discussed briefly.     

Sesquiterpene lactones from Brachylaena species

The investigation of two Brachylaena species afforded in addition to known sesquiterpene lactones and other constituents five new lactones, a germacranolide, a guaianolide and three eudesmanolides. The structures were elucidated by spectroscopic methods. The chemotaxonomy of this complex genus is discussed.     

Further eudesmanolides and xanthanolides from Telekia speciosa

The re-investigation of the aerial parts of Telekia speciosa afforded five new sesquiterpene lactones, two eudesmanolides and three xanthanolides, all closely related to those isolated before from this species or from related genera. The structures were elucidated by ¹H NMR spectroscopy.     

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.     

Guaianolides from Ainsliaea fragrans

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

A new type of germacranolide from Vernonia species

From several South African Vernonia species, a considerable number of sesquiterpene lactones has been isolated. Together with known compounds, seven members of a new type with an enol lactone ring have been found, their structures being elucidated by spectroscopic methods and some chemical transformations. Furthermore two new derivatives of costunolide are present in two species, and three new guaianolides have been found. From some species, however, no lactones could be isolated. Together with a new bisabolene derivative, a known eremophilone has been isolated, probably for the first time, from a member of the tribe Vernonieae.     

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.     

Three bourbonenolides and other sesquiterpene lactones from two vernonia species

A re-investigation of V. arkansana afforded several new sesquiterpene lactones, three bourbonenolides, obviously closely related to those isolated from this plant previously, a glaucolide and a methoxy derivative most probably formed by fragmentation of the corresponding bourbonenolide. From V. profuga in addition to known lactones a new guaianolide was isolated. The biogenetic relationships of the Vernonia sesquiterpene lactones are discussed briefly.     

Pseudoguaianolides and other sesquiterpene lactones from Gaillardia species

The aerial parts of two Gaillardia species afforded in addition to known sesquiterpene lactones 23 new pseudoguaianolides, two dugaldiolide derivatives and two seco-neopulchellin derivatives. The structures were elucidated by spectroscopic methods. Biogenetic relationships are discussed briefly.     

Five mikanolide derivatives from mikania cynanchifolia and their biogenetic relationships

The investigation of the aerial parts of Mikania cynanchifolia afforded, in addition to miscandenin, five new sesquiterpene lactones, miscandenin-1,2-epoxide, an isomiscandenin and three further dilactones related to mikanolide. The structures of these new compounds were elucidated by high field ¹H NMR spectroscopy. The biogenetic relationships of the sesquiterpene lactones are briefly discussed.     

Eriolanolides,eudesmanolides and a rearranged sesquiterpene from Eriophyllum species

The investigation of two Eriophyllum species afforded, in addition to numerous known compounds, eight new sesquiterpene lactones related to eriolanin, two eudesmanolides and a new type of sesquiterpene alcohol. The structures were elucidated by spectroscopic methods and a few chemical transformations. The chemotaxonomic situation of this genus, the placement of which is still in doubt, is discussed briefly.     

Oxepane diterpenoids sesquiterpene lactones from ‘zoapatle’ (montanoa tomentosa), a mexican plant with oxytocic activity

Investigation of the ‘tea’ prepared from the leaves of ‘zoapatle’ (Montanoa tomentosa), resulted in the isolation of the known biologically active oxepane diterpenoids zoapatanol and montanol, the known sesquiterpene lactones zoapatanolide A, C and D as well as two new biologically active oxepane diterpenoids and a new sesquiterpene lactone. The structures of the new compounds were established by spectroscopic methods.     

Terpenoids and bibenzyls of 25 liverwort Frullania species

Twenty-five Frullania species (liverworts) were chemically investigated. Fourteen species produce allergy-inducing sesquiterpene lactones. Eighteen species contain bibenzyls. The sesquiterpene lactones and bibenzyls are obtained as the major components and they are valuable chemosystematic markers of Frullania species. On the basis of their chemical constituents, Frullania species can be divided into five chemotypes: sesquiterpene lactone-bibenzyl type; sesquiterpene lactone type; bibenzyl type; monoterpene type and cyclocolorenone type.     

Germacranolides from Helianthus californicus

Five germacranolide sesquiterpene lactones and a trachylobane diterpene were isolated from the hexaploid species Helianthus californicus. Four of the sesquiterpene lactones are new, including a 1-oxo-3,10-diol without any carbon-carbon double bonds in the main ring whose structure was confirmed by X-ray crystallography. These results require revision of the structures of several previously published compounds. Two of the germacranolides have alkyl ether functions at a position β to a ketone and are believed to be artifacts of the isolation process. Based on terpenoid chemistry, there are no obvious progenitors of H. californicus among the diploid species of Helianthus examined to date.