Seven sesquiterpene lactones from Ferreyanthus species

The investigation of two Ferreyanthus species afforded seven germacranolides which have not been isolated previously. Two derivatives of linalol were also present. The structures were elucidated by spectroscopic methods. Chemotaxonomic relationships are briefly discussed.     

Ant-repellent sesquiterpene lactones from Eupatorium quadrangularae

The chloroform extract from the leaves of Eupatorium quadrangularae has been systematically fractionated by following biological activity in a bioassay which measures repellency to the leafcutter ant Atta cephalotes (Formicidae, Attini). Several sesquiterpene lactones were isolated, two of which showed significant ant-repellency.     

Ineupatorolide-like sesquiterpene lactones from Dittrichia viscosa

Dittrichia viscosa afforded, in addition to known compounds, minute amounts of nine sesquiterpene lactones, all closely related to ineupatorolide B     

Two sesquiterpene lactones from Trichogonia gardneri

The structures and stereochemistries of two sesquiterpene lactones from Trichogonia gardneri were established as (6R,7S,8S,9S,IOR)-4E-9,10-dihydroxy-8-tigloxygermacr-4-en-6,12-olide) and (5R*,6R*,7S*,8S*,9R*)-14-acetoxy-3-chloro-9-hydroxy-2-oxo-8-tigloxyguia-1(10),3-dien-6,12-of olide by a combination of NMR spectrometry and X-ray diffraction. The results show that the structures of several sesquiterpene lactones which were isolated previously from related species require revision.     

Glaucolide-like sesquiterpene lactones from Cotula cinerea

The aerial parts of Cotula cinerea gave, in addition to widespread compounds, a characteristic diacetylenic spiroketal enolether and several sesquiterpene lactones, three of them being glaucolide-like lactones. The structures were elucidated by highfield ¹H NMR spectroscopy.     

New types of sesquiterpene lactones and other constituents from Trichogonia species

The investigation of five Trichogonia species afforded seven new furanoheliangolides, three dilactones of a new type, four pairs of epimeric rearra     

Two sesquiterpene lactones from artemisia species

Two new sesquiterpene lactones, himeyoshin and montanone, were isolated from Artemisia feddei and A. montana, respectively and identified by chemical and spectral data as1α,2α-epoxy-3-oxo-5,6-dihydroalantolactone and 1,10-dihydro-11,13-dehydromatricarin.     

Further sesquiterpene lactones from Calea and Viguiera species

The aerial parts of Calea clematidea gave three new germacranolides, those of Viguiera procumbens two orizabin derivatives and those of V. linearis dihydrobudlein A. In addition to these lactones, several known ones were isolated.     

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.     

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.     

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.     

The first sesquiterpene lactones esterified with a sesquiterpenic acid

From Hypochoeris glabra two guaianolides esterified with an unusual sesquiterpenic acid were isolated. Proton-catalysed rearrangement of the cyclopropane derivative led to a phenolic acid. The structures were elucidated by high-field ¹H NMR spectroscopy. Further guaianolides were isolated from H. uniflora and Lactuca floridana. These structures were elucidated by spectroscopic methods. The chemotaxonomic situation in the tribe is discussed briefly.     

Minor sesquiterpene lactones of Helianthus pumilus

The isolation of four known and two new germacradienolides and one known heliangolide from Helianthus pumilus, in addition to the previously report     

Two sesquiterpene lactones from Centaurea canariensis

From the aerial part of Centaurea canariensis three sesquiterpene lactones were isolated: cynaropicrin, deacylcynaropicrin and aguerin A. The same species, grown from seed, yielded cynaropicrin, deacylcynaropicrin and aguerin B. The guaianolides aguerin A and B are reported for the first time. Aguerin B was subsequently found to be present in Centaureana linifolia, C. canariensis (var subspinnata) and C. sventenii.     

New sesquiterpene lactones from Artemisia herba alba

The structures of herbolides A, B and C, new sesquiterpene lactones isolated from Artermisia herba alba, were determined by chemical and spectroscopic methods.     

Two sesquiterpene lactones of Calea ternifolia var. Calyculata

Chemical analysis of Calea ternifolia var. calyculata yielded the known sesquiterpene lactone calein A, as well as two new modified heliangolid     

Biological activities of sesquiterpene lactones

Sesquiterpene lactones are characteristic constituents of the Compositae but also occur sporadically in other angiosperm families and even in some liverworts. These bitter substances often contain as a major structural feature an α,β-unsaturated-γ-lactone, which in recent studies has been shown to be associated with anti-tumor, cytotoxic, anti-microbial and phytotoxic activity. They are known to poison livestock, to act as insect feeding deterrents and to cause allergic contact dermatitis in humans. This review highlights the present state of knowledge on the biological activities and mechanism of action of some sesquiterpene lactones.     

Systematic implications of flavonoids and sesquiterpene lactones in species of Vernonia

Systematic and evolutionary interpretations based upon the distributional data for 27 flavonoids from 39 species and 9 sesquiterpene lactones from 38 species are presented for species of Vernonia mostly from the New World.     

Diterpenes and sesquiterpene lactones from Mikania congesta

The chloroform extract of the aerial parts of Mikania congesta, afforded four new geranylnerol derivatives, new analogs of deoxyelephantopin, a new melampolide and several known compounds. Structures were elucidated by spectroscopic methods and chemical transformations.     

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.