Pseudoguaianolides carabrone derivatives from Loxothysanus sinuatus

The aerial parts of Loxothysanus sinuatus afforded in addition to known compounds nine new pseudoguaianolides, three guaianolides and five carabrone derivatives. The structures were elucidated by spectroscopic methods. The chemotaxonomy is discussed briefly. The configurations of two guaianolides were corrected.     

Dimeric guaianolides from Artemisia sieversiana

The aerial parts of Artemisia sieversiana afforded in addition to known compounds five new guaianolides and four dimeric guaianolides, three of them closely related to absinthin and one derived from estafiatin as a monomer. The structures were elucidated by extensive NMR studies, which allowed the assignment of the 14 chiral centres. Artemisia frigida afforded several known compounds and one new guaianolide, 8-desoxy-cumambrin B, the most likely precursor of many guaianolides.     

A new guaianolide glucoside from aerial parts of Lactuca aculeata

From aerial parts of Lactuca aculeata one new and ten known sesquiterpene lactone aglycones and glycosides were isolated, including four lactucin-type guaianolides, six costus lactone-type guaianolides and one melampolide-type germacranolide. The structure of the new compound was determined as 11β-hydroxycrepidiaside B by high resolution mass spectrometry and 1D- and 2D-NMR spectroscopy.     

Dehydrocostuslactone and plant growth activity of derived guaianolides

The stereostructures of two new guaianolides, isodehydrocostuslactone and isozaluzanin C, isolated previously from Saussurea lappa, have been confirmed by their correlation with dehydrocostuslactone. Twenty new derivatives have been synthesized from these guaianolides and these have been tested as plant growth regulators. The conjugated lactones which have an exocyclic methylene group at C-4 conjugated with a C-3 ketone, show distinct enhancement in their root-forming potential, as compared with their 3-deoxy derivatives. Of further significance is the fact that these ketones display maximum activity only at lower concentrations. Other compounds show the expected structure-biological activity relationships displayed in general by guaianolides. However, the presence of an epoxide at the C-3, C-4 position does not affect the biological activity, which is indeed the case when the epoxide group occupies the C-4, C-14 position in guaianolides. The major biological parameter studied was rooting in-stem cuttings of Phaseolus aureus.     

Guaianolides in apiaceae: perspectives on pharmacology and biosynthesis

The guaianolide group of sesquiterpene lactones contains a large number of compounds with biological activity. One of these guaianolides, thapsigargin from the genus Thapsia (Apiaceae), has been a subject of particular interest in recent years because of its ability to induce apoptosis, as the active part of a pro-drug, has produced promising results for the targeted treatment of prostate cancer. In this review, recent advances in understanding the biosynthetic pathway of sesquiterpenes in plants is described with a special emphasis on guaianolides, and a hypothetical pathway for the biosynthesis of thapsigargin is presented. Eighty-seven guaianolides from Apiaceae are presented. These compounds provide clues to possible enzymatic mechanisms generating the guaianolides in Apiaceae. Some of these 87 compounds have proven or might prove interesting with regards to their biological activity.     

Absolute stereochemistry of guaianolides, of matricin and its epimers, of yarrow proazulenes, and of chamazulene carboxylic acid

Known determinations of the absolute configuration of guaianolides were collected and found to be few. The absolute configurations of guaianolides rest on the assumption that 7-H always has alpha-orientation. For matricin, only the relative configuration was determined. On the basis of a detailed study of the NMR spectra of matricin and its epimers, and of synthetic, NMR, and CD studies with its decomposition product, chamazulene carboxylic acid, we were able to reconfirm the accepted 3S,3aR,4S,9R,9aS,9bS configuration of matricin.     

Sesquiterpene lactones of eupatorium anomalum and eupatorium mohrii

Several new guaianolides and the previously known heliangolide eurecurvin have been isolated from Eupatorium anomalum. Eupatorium mohrii also yielded three of the new guaianolides together with eurecurvin and a new germacradienolide. The implications of these findings are discussed.     

Dimeric guaianolides and other constituents from Gochnatia species

The roots of Gochnatia polymorpha afforded two new bisabolene derivatives and four dimeric guaianolides, two of them being isolated previously from G. paniculata. The aerial parts gave two further dimeric guaianolides. The aerial parts of G. hypoleuca afforded three new germacran-8,12-olides, a germacranolide acid and four additional dimeric guaianolides, which may be characteristic for this genus, while the presence of oxygenated germacranolides seems to be typical for the whole subtribe.     

New germacranolides,guaianolides and rearranged Guaianolides from Lasiolaena santosii

The aerial parts of L. santosii afforded three new diterpenes, a phenylpropanol, three eudesmane derivatives, three germacranolides, seventeen guaianolides and four rearranged guaianolides of a, so far, unknown type. Furthermore, several known compounds were isolated. The structures of the new compounds, the separations of which caused difficulties, were elucidated by spectroscopic methods and by some chemical transformations. The chemotaxonomic situation is discussed briefly.     

Further sesquiterpene lactones from Anthemis carpatica

A new germacranolide, (E)-1alpha, 10beta-epoxy-3beta-acetoxy-6alpha-hydroxygermacra-4,11 (13)-dien-12,8alpha-olide, together with nine new highly oxygenated guaiadien-12,6alpha-olides of anthemolide, and cumambrin type were identified in the repeated examination of the aerial parts of the flowering Anthemis carpatica. In addition, six known guaianolides belonging to the same groups, also isolated previously from A. carpatica, along with two guaianolides, 2beta-hydroxyepiligustrin and cumambrin B, not found before in this species, were isolated this time.     

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.     

Structure of histamine releasing guaianolides from Thapsia species

The structures of six hexaoxygenated guaianolides esterified with four non isomeric carboxylic acids have been established by ¹H NMR and ¹³C NMR spectroscopy. The acyl residues have been located by chemical ionisation mass spectrometry. Some of the acyl residues are novel for sesquiterpene lactones. The acyl residues in two additional guaianolides esterified with isomeric acids have been located by partial hydrolysis.     

Further guaianolides and 5-alkylcoumarins from gutenbergia and bothriocline species

From Gutenbergia marginata ten new guaianolides were isolated. Two guaianolides isolated previously from Erlangea inyangana are identical with two further lactones and their structures have been revised. From Bothriocline ripensis ethulia coumarin and two further 5-alkylcoumarin derivatives, one being a chromone, were isolated, while B. longipes and B. eupatorioides gave nine 5-alkylcoumarins and two related compounds. The structures were elucidated by highfield NMR techniques and a few chemical transformations.     

Sesquiterpenes and flavonoid aglycones from a Hungarian taxon of the Achillea millefolium group

The investigation of a dichloromethane extract of flower heads of a Hungarian taxon of the Achillea millefolium group led to the isolation of three flavonoid aglycones, one triterpene, one germacranolide and five guaianolides. Their structures were elucidated by UV-VIS, EI- and CI-MS, 1H NMR and 13C NMR spectroscopic methods as well as by 2D-NMR studies and by selective 1D-NOE experiments. Besides apigenin, luteolin and centaureidin, beta-sitosterol, 3beta-hydroxy-11alpha,13-dihydro-costunolide, desacetylmatricarin, leucodin, achillin, 8alpha-angeloxy-leucodin and 8alpha-angeloxy-achillin were isolated. Both latter substances are reported here for the first time. Their NMR data were compared with those of the other guaianolides. The stereochemistry of 3beta-hydroxy-11alpha,13-dihydro-costunolide was discussed and compared with data of the literature.     

Sesquiterpene lactones from Anthemis carpatica Willd

Four new eudesmanolides and two new guaianolides were isolated from the aerial parts of Anthemis carpatica Willd. and their structures elucidated by spectral methods. In addition, seven known sesquiterpene lactones were identified.     

Guaianolides from the leaves of Centaurea incana

Six guaianolides have been isolated from the aerial parts of Centaurea incana from Algeria. They were identified as desoxyrepin, repin or subluteolide, repin monochlorhydrin, acroptilin, janerin and repdiolide triol.     

Guaianolides from elephantopus carolinianus

The roots of Elephantopus carolinianus afforded two guaianolides as well as two known elephantopin derivatives which were the main constituents of the aerial parts.     

Guaianolides from Gochnatia smithii

The structure and stereochemistry of 8α-acetoxy and 8α-tigloyloxy dehydrocostus lactones, two guaianolides isolated from the aerial parts of Gochnatia smithii, were established by chemical and spectroscopic methods.     

Guaianolides from Centaurea canariensis

The aerial parts of Centaurea canariensis afforded four new guaianolides, all closely related to dehydrocostus lactone, and a derivative of costic acid. The structures were elucidated by spectroscopic methods.