Chemical Composition of Laurencia obtusa Extract and Isolation of a New C15-Acetogenin.

A new C15-acetogenin, sagonenyne (20), exhibiting an unusual single tetrahydropyran ring was isolated from an ethyl acetate extract of Laurencia obtusa collected on the Corsican coastline. Its structure was established by detailed NMR spectroscopic analysis, mass spectrometry, and comparison with literature data. Twenty-three known compounds were identified in the same extract by means of column chromatography steps, using a 13C-NMR computer aided method developed in our laboratory. In addition to sesquiterpenes, which represent the main chemical class of this extract, diterpenes, sterols, and C15-acetogenins were identified. The crude extract was submitted to a cytotoxicity assay and was particularly active against THP-1 cells, a human leukemia monocytic cell line.

Quantification of taxanes in a leaf and twig extract from Taxus baccata L. using 13C NMR spectroscopy.

In the course of our ongoing work on the chemical characterization of Taxus baccata L. growing wild in Corsica, we have developed and validated a method for direct quantification of taxane derivatives by (13)C NMR using 10-deacetylbaccatin III as reference compound and 1,6-hexanediol as internal standard. We have observed good accuracy (relative errors between 0.3% and 3.5%), linearity (R(2) = 0.999) and precision (reproducibility 8.5 mg ± 1.1%) of the measurements. The experimental procedure was applied to the quantification of six identified taxanes in a fraction of chromatography of a methanol extract of T. baccata leaves. This method can be applied to other compounds bearing the taxane skeleton.

Chemical variability of Algerian Myrtus communis L.

The composition of 55 samples of essential oil isolated from the aerial parts of wild growing Myrtus communis L. harvested in 16 locations from East to West Algeria were investigated by GC (determination of retention indices) and (13) C-NMR analyses. The essential oils consisted mainly of monoterpenes, α-pinene (27.4-59.2%) and 1,8-cineole (6.1-34.3%) being the major components. They were also characterized by the absence of myrtenyl acetate. The compositions of the 55 oils were submitted to k-means partitioning and principal component analysis, which allowed the distinction of two groups within the oil samples, which could be subdivided into two subgroups each. Groups I (78% of the samples) and II were differentiated on the basis of the contents of α-pinene, linalool, and linalyl acetate. Subgroups IA and IB could be distinguished by their contents of α-pinene and 1,8-cineole. Subgroups IIA and IIB differed substantially in their contents of 1,8-cineole and limonene. All the samples contained 3,3,5,5,8,8-hexamethyl-7-oxabicyclo[4.3.0]non-1(6)-ene-2,4-dione (up to 4.9%).

Chemical variability of the leaf essential oil of Xylopia aethiopica (Dunal) A.Rich. from Côte d'Ivoire.

The chemical composition of 48 essential-oil samples isolated from the leaves of Xylopia aethiopica harvested in six Ivoirian forests was investigated by GC-FID and (13) C-NMR analyses. In total, 23 components accounting for 82.5-96.1% of the oil composition were identified. The composition was dominated by the monoterpene hydrocarbons ß-pinene (up to 61.1%) and α-pinene (up to 18.6%) and the sesquiterpene hydrocarbon germacrene D (up to 28.7%). Hierarchical cluster and principal component analyses allowed the distinction of two groups on the basis of the ß-pinene and germacrene D contents. The chemical composition of the oils of Group I (38 oil samples) was clearly dominated by ß-pinene, while those of Group II (10 samples) were characterized by the association of ß-pinene and germacrene D. The leaves collected in the four inland forests produced ß-pinene-rich oils (Group I), while the oil samples belonging to Group II were isolated from leaves harvested in forests located near the littoral.

Chemical variability of the wood essential oil of Cedrus atlantica Manetti from Corsica.

The composition of 48 samples of essential oil isolated from the wood of Cedrus atlantica growing in Corsica was investigated by GC (in combination with retention indices), GC/MS, and (13) C-NMR. Twenty-three compounds accounting for 73.9-96.0% of the oil composition were identified. The oils consisted mainly of monoterpene hydrocarbons and sesquiterpenes, in particular α-pinene (5; up to 79.4%), himachalol (4; up to 66.2%), ß-pinene (up to 21.4%), ß-himachalene (2; up to 19.3%), γ-himachalene (3; up to 11.0%), and α-himachalene (1; up to 10.9%). The 48 oil compositions were submitted to k-means partitioning and principal-component analysis, which allowed the distinction of two groups within the oil samples. The composition of Group I (44% of the samples) was dominated by 5, while the samples of Group II (56% of the samples) contained mainly 4.

Self-diffusion coefficients obtained from proton-decoupled carbon-13 spectra for analyzing a mixture of terpenes.

In the limit of sufficient sensitivity, natural abundance 13C offers a much better spectral resolution than proton NMR. This is due to an important chemical shift range and to proton-decoupling conditions that yield one peak per carbon with practically no overlap. However, pulsed gradient spin echo experiments, which lead to the diffusion coefficient associated with each peak, have scarcely been employed. In this article, we present and compare different ways to access this quantity and we have effectively verified that, without any precaution, diffusion coefficients cannot be properly determined from standard procedures. The cause of such a failure is decoupling during the gradient pulses. We have used a very simple remedy that proved to be very successful on a model mixture of three monoterpenes and that appears as being of general applicability.

Identification of taxanes in extracts from leaves of Taxus baccata L. using (13)C-NMR spectroscopy.

INTRODUCTION: The study of taxanes is a hot topic worldwide because of their potential activity against cancer. Analysis of taxanes in extracts of various Taxus species is generally achieved using HPLC. OBJECTIVE: The aim of the current work was to identify taxanes in different fractions of extracts from Taxus baccata L. using the computer-aided analysis of their( 13)C-NMR spectra. METHODOLOGY: A computerised procedure, based on (13)C-NMR spectroscopy using literature data, has been developed in order to identify taxoids in natural mixtures. Leaves and twigs of T. baccata were extracted with various solvents and the extracts were fractionated according to rapid fractionation schemes described in the literature. RESULTS: The computer-assisted analysis of the (13)C-NMR spectra of the fractions of chromatography led to the identification of 16 taxanes belonging to the taxine, taxicine, taxinine and taxuspine families. CONCLUSION: It has been shown that (13)C-NMR is a powerful alternative tool for the identification of taxanes in extracts of leaves and twigs of various Taxus species after a rapid fractionation step.

Identification and quantitative determination of carbohydrates in ethanolic extracts of two conifers using 13C NMR spectroscopy.

We developed a method for the direct identification and quantification of carbohydrates in raw vegetable extracts using (13)C NMR spectroscopy without any preliminary step of precipitation or reduction of the components. This method has been validated (accuracy, precision and response linearity) using pure compounds and artificial mixtures before being applied to authentic ethanolic extracts of pine needles, pine wood and pine cones and fir twigs. We determined that carbohydrates represented from 15% to 35% of the crude extracts in which pinitol was the principal constituent accompanied by arabinitol, mannitol, glucose and fructose.

Supercritical CO2 extract from needles of Pinus nigra ssp. laricio: combined analysis by GC, GC-MS and 13C NMR.

The chemical composition of the volatile concentrate prepared by supercritical CO(2) extraction of the needles of Pinus nigra Arnold ssp. laricio Poiret from Corsica was investigated using GC (RI), GC-MS and (13)C NMR spectroscopy. The major component was by far manoyl oxide (63%), a compound of potential interest for the perfumery and pharmaceutical industries. Consequently, the supercritical fluid extract of P. nigra ssp. laricio (yield 1.60%) could be considered as a source of this diterpene.

Composition and Variability of Leaf Oil from Monodora crispata - ¹³C NMR Identification of Heat-sensitive Compounds.

The composition of four samples of essential oil isolated from the leaves of individual Monodora crispata trees growing wild in an Ivorian forest (Adiopodoum6) were investigated by a combination of chromatographic (GC(RI)) and spectrometric (GC-MS, "C NMR) techniques. In total, fifty-seven compounds accounting for 92.3-98.7% of the whole composition were identified. These oils were characterized by the preeminence of sesquiterpene hydrocarbons and the content of the main components varied substantially from sample to sample. Two samples were largely dominated by germacrene D (67.3% and 76.3%, respectively), a third sample was represented by germacrene D (28.3%), germacrene C (14.3%), δ-elemene (12.1%) and ß-elemene (9.3%) and the fourth sample was characterized by 3-dimethylallylindole (15.1%), germacrene D (12.0%) and cyperene (7.8%). C NMR spectroscopy was particularly efficient for the identification of heat-sensitive compounds.

Identification and quantitative determination of lignans in Cedrus atlantica resins using 13C NMR spectroscopy.

Identification and quantitative determination of individual components of resin collected on the trunk of 28 Cedrus atlantica trees, grown in Corsica, has been carried out using 13C NMR spectroscopy. Eight resin acids bearing either the pimarane or abietane skeleton, two monoterpene hydrocarbons and four oxygenated neutral diterpenes have been identified, as well as three lignans, scarcely found in resins. Three groups could be distinguished within the 28 resin samples. The nine samples of Group I had their composition dominated by diterpene acids (33.7-45.8%), with abietic acid (6.2-18.7%) and isopimaric acid (5.1-12.6%) being the major components. The four samples of Group II contained resin acids (main components) and lignans in moderate amounts (up to 10.3%). Conversely, lignans (38.8-63.8%) were by far the major components of the 15 samples of Group III. Depending on the sample, the major component was pinoresinol (18.1-38.9%), lariciresinol (17.2-33.7%) or lariciresinol 9'-acetate (16.9-29.1%). Finally, due to the high biological interest in lignans, a rapid procedure, based on 1H NMR spectroscopy, was developed for quantification of lignans in resins of C. atlantica.

Combined analysis by GC (RI), GC-MS and 13C NMR of the supercritical fluid extract of Abies alba twigs.

Two samples (leaves and twigs) of Abies alba Miller from Corsica were extracted using supercritical CO2 and their chemical compositions were compared with those of the essential oils obtained from the same batch of plant material. In total 45 components were identified using combined analysis by GC (RI), GC-MS and 13C NMR. It was observed that the contents of monoterpenes (mainly represented by limonene, alpha-pinene and camphene) were significantly lower in the supercritical fluid extract (SFE) than in the essential oil (EO). Conversely, the proportions of sesquiterpenes were much higher in CO2 extracts than in essential oils (around 30% vs 4%). Cis-abienol, a diterpene alcohol, was identified only in SFE, and the proportions of this constituent (7.5% and 17.3%) were determined using quantitative 13C NMR since it was under estimated using the standard conditions of GC.

Triterpenes in the hexane extract of leaves of Olea europaea L.: analysis using 13C-NMR spectroscopy.

Two neutral triterpenes and a triterpene acid were identified and quantified directly, in the absence of any purification steps, in a precipitate obtained during the industrial extraction of the leaves of Olea europaea L. using 13C-NMR spectroscopy (spectrometer operating at 4.7 T equipped with a 10 mm probe). The method was optimised in order to reduce the duration of analysis with a routine NMR spectrometer. Together with long-chain linear compounds, erythrodiol, uvaol and oleanolic acid accounted for 27.3, 18.3 and 12.5% of the precipitate, respectively.