Eudesmane and rearranged eudesmane sesquiterpenes from Nectandra cissiflora

Four eudesmane-type sesquiterpenes, costic acid (1), 12-carboxyeudesman-3,11(13)-diene (2), viscic acid (3), 3-oxo-γ-costic acid (4) and two rearranged eudesmane derivatives, 3α-hydroxyisoiphion-11(13)-en-12-oic acid (5) and 5β-hydroxy-4-oxo-11(13)-dehydroiphionan-12-oic acid (6), in addition to (-)-epicatechin, have been isolated from the trunk bark of Nectandra cissiflora. This is the first reported occurrence in the Lauraceae of 3-6. The structures of the isolated compounds have been established on the basis of 1D and 2D NMR spectroscopic techniques. The 13C NMR assignments of 3, 5 and 6 are given here for the first time, as well as some corrections to the previously reported chemical shift assignments of 4.

Benzylisoquinoline alkaloids and eudesmane sesquiterpenes from Ocotea pulchella

Bark of Ocotea pulchella contains, besides 1-(p-methoxybenzoyl)-6,7-methylenedioxyisoquinoline, 1-(hydroxy-p-methoxybenzyl)-6,7-methylenedioxyisoquinoline and their 1,2-dihydro-derivatives, 11-eudesmen-4α-ol and 4-furanoeudesmen-6-one. © 1993.

Eudesmanolides and Methyl Ester Derivatives from Dimerostemma arnottii

The phytochemical investigation of Dimerostemma arnottii (Asteraceae) afforded, in addition to a known eudesmanolide, two unusual eudesmane methyl ester derivatives and a new eudesmanolide. Structural elucidation of the compounds was based on their ID and 2D NMR spectroscopic as well as HR-ESI-MS data. There is a remarkable similarity between the structures of the eudesmanes from D. arnottii and those previously encountered in other Dimerostemma species, which is in agreement with the results of a previous phylogenetic study based on molecular data. The chemotaxonomic relevance of the isolated compounds is briefly discussed.

Sesquiterpenos de sementes de Guarea guidonia (Meliaceae)

Two new sesquiterpenes 6α-ethoxyeudesm-4(15)-en-1β-ol (1) and (7R*)-5-epi-opposit-4(15)-ene-1β,7-diol (7) were isolated from the seeds of a specimen of Guarea guidonia (Meliaceae). Five other known sesquiterpenes, eudesm-4(15)-ene-1β,6α-diol (2), 5-epi-eudesm-4(15)-ene-1β,6β-diol (3), eudesm-4(15)-ene-1β,5α-diol (4), eudesm-4(15),7-dien-1β-ol (5) and (7R*)-opposit-4(15)-ene-1β,7-diol (6), were also isolated in this work. Their structures were determined on the basis of spectral data (MS, IR, and NMR-1D and 2D) and subsequent comparisons with the literature. The substances 3, 4 and 6 are reported for the first time in Meliaceae and 5 for the first time in the genus Guarea.

Minor sesquiterpenes from the volatile oil from leaves of Guarea guidonia Sleumer (Meliaceae)

The essential oil from leaves of Guarea guidonia was subjected to chromatographic separation procedures to afford nine sesquiterpenes; two of them are new eudesmane derivatives. The chemical structures of the obtained compounds were characterised by spectrometric analysis, mainly mass spectrometry and NMR.

(+)-Germacrene A Biosynthesis : The Committed Step in the Biosynthesis of Bitter Sesquiterpene Lactones in Chicory

The leaves and especially the roots of chicory (Cichorium intybus L.) contain high concentrations of bitter sesquiterpene lactones such as the guianolides lactupicrin, lactucin, and 8-deoxylactucin. Eudesmanolides and germacranolides are present in smaller amounts. Their postulated biosynthesis through the mevalonate-farnesyl diphosphate-germacradiene pathway has now been confirmed by the isolation of a (+)-germacrene A synthase from chicory roots. This sesquiterpene cyclase was purified 200-fold using a combination of anion-exchange and dye-ligand chromatography. It has a Km value of 6.6 μm, an estimated molecular mass of 54 kD, and a (broad) pH optimum around 6.7. Germacrene A, the enzymatic product, proved to be much more stable than reported in literature. Its heat-induced Cope rearrangement into (−)-β-elemene was utilized to determine its absolute configuration on an enantioselective gas chromatography column. To our knowledge, until now in sesquiterpene biosynthesis, germacrene A has only been reported as an (postulated) enzyme-bound intermediate, which, instead of being released, is subjected to additional cyclization(s) by the same enzyme that generated it from farnesyl diphosphate. However, in chicory germacrene A is released from the sesquiterpene cyclase. Apparently, subsequent oxidations and/or glucosylation of the germacrane skeleton, together with a germacrene cyclase, determine whether guaiane- or eudesmane-type sesquiterpene lactones are produced.