Mathieu Paoli

Identification of taxanes in extracts from leaves of Taxus baccata L. using 13C-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.

Chemical Variability of the Wood Essential Oil of Cedrus atlanticaManetti 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 13C‐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%), β‐pinene (up to 21.4%), β‐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.

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 13C 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 (R2 = 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. Copyright

Chemical composition of Melicope belahe (Baill.) T. G. Hartley (Rutaceae) leaf essential oil from Madagascar

Abstract Melicope belahe (Baill.) T.G. Hartley (Rutaceae) is an endemic species to Madagascar. The chemical composition of leaf essential oil is reported for the first time. A sample was extracted by hydrodistillation and analysis was carried out by combination of chromatographic (GC), spectroscopic and spectrometric (MS, 13C NMR) techniques. In total, 56 compounds have been identified. The chemical composition was dominated by α-pinene (42.6%) followed by linalool (6.2%) and (E)-β-caryophyllene (5.2%). Graphical Abstract

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.

Chemical composition of leaf and bark essential oils of Vepris unifoliolata from Madagascar

Abstract The chemical composition of leaf essential oil of Vepris unifoliolata was characterized by hydrocarbon monoterpenes, α-pinene (60.5%), myrcene (6.8%), limonene (5.1%), (E)-β-ocimene (4.9%) and β-phellandrene (4.7%). The chemical composition of bark essential oil of V. unifoliolata was original and characterized by a high content in heat-sensitive compounds isofuranodiene (43.9%) and germacrone (17.1%). These compounds bearing the (E,E)-1,5-cyclodecadiene structure were known to rearrange and degrade during the GC–FID and GC-MS. The true content of isofuranodiene/curzerene, germacrone/trans-β-elemenone, germacrene A/β-elemene and germacrene B/γ-elemene was evaluated by combination of 13C-NMR data (intensities of signals of selected carbons) and GC–FID. Thus, a correct quantitative analysis of bark oil of V. unifoliolata was provided.

Chemical composition of the leaf essential oil of grapefruits (Citrus paradisi Macf.) in relation with the genetic origin

Abstract The composition of twenty-four samples of essential oil isolated from leaves of Citrus paradisi Macf. growing in a northern area of citrus cultivation in Mediterranean climate (Corsica) was investigated by GC (RI), GC-MS and 13C NMR. Thirty-six compounds accounting for 94.9–99.3% of the oil composition were identified. The oils contained mainly monoterpene hydrocarbons and specially sabinene (up to 60.2%),(E)-β-ocimene (up to 15.0%) and punctually γ-terpinene (up to 56.1%), β-pinene (up to 30.9%) and p-cymene (up to 12.5%). The twenty-four compositions were submitted to k-means partitioning and principal component analysis, which allowed the distinction of one homogeneous group of twenty-two grapefruits (main compound sabinene, mean = 47.1%).This group included eighteen cultivars derived by mutation from the ancestral grapefruit tree (Duncan) and four cultivars known to be interspecific hybrids. Two out group cultivars were clearly differentiated from others by original chemical compositions, in agreement with their hybrid origin.

Chemical composition of the essential oils from the aerial parts of two Malagasy endemic species (Apiaceae): Billburttia capensoides Sales & Hedge and Billburttia vaginoides Sales & Hedge

Abstract The chemical composition of twenty-five essential oil samples from the aerial parts of two Malagasy endemic species Billburttia capensoides Sales & Hedge and B. vaginoides Sales & Hedge, were investigated for the first time. Based on chromatographic profiles, three selected samples were investigated using GC(RI), GC-MS and 13C NMR. The content of the main components varied drastically from sample to sample: p-mentha-1,3,8-triene (0.2–52.7%), terpinolene (2.8–40.7%) and dill apiole (0.0–22.2%). Statistical analysis of the 25 oil compositions allowed the distinction of two well-differentiated groups. Samples of group I contained mainly p-mentha-1,3,8-triene while the Group II was dominated by terpinolene and dill apiole.

Anti-Quorum Sensing Activity of 12 Essential Oils on chromobacterium violaceum and Specific Action of cis-cis-p-Menthenolide from Corsican Mentha suaveolens ssp. Insularis

Quorum sensing (QS) is a bacterial communication mechanism used to express various survival or virulence traits leading to enhanced resistance. Chromobacterium violaceum is a commonly used strain that highlights anti-QS action of bioactive substances. Here, we wanted to see if 12 selected essential oils (EO) could exert anti-QS activity. We measured the sublethal minimal QS inhibitory concentration (MQSIC) by assessing violacein production of C. violaceum along with bacterial growth. To confirm the QS disruption, we also proceed to surface bacterial observations using scanning electron microscopy (SEM). We showed that cis-cis-p-menthenolide extracted and isolated from a plant endemic to occidental Mediterranean Sea islands, Mentha suaveolens ssp. insularis, acts as an inhibitor of violacein production and biofilm formation. Measured MQSIC was much lower than the minimal inhibitory concentration (MIC): 0.10 mg·mL−1 vs. 3.00 mg·mL−1. Moreover, disturbance of QS-related traits was confirmed by the degradation of C. violaceum biofilm matrix. There is a clear structure–activity relationship between cis-cis-p-menthenolide and anti-QS activity. Indeed, its isomer molecule (mintlactone) exerts a poor anti-QS action. These results indicate that inhibition of violacein production and biofilm formation by cis-cis-p-menthenolide might be related to a disruption in the QS mechanism.

Composition and Chemical Variability of Enantia polycarpa Engl. & Diels Leaf Essential Oil from Côte d'Ivoire

The composition of Enantia polycarpa Engl. & Diels leaf essential oil has been investigated for the first time using a combination of chromatographic and spectroscopic techniques. The compositions of 52 leaf essential oil samples have been subjected to statistical analysis, hierarchical cluster analysis (HCA) and principal component analysis (PCA). Four groups were differentiated, of which the compositions were dominated by β‐elemene and germacrene B (Group III, 22/52 samples); germacrene D (Group I, 16/52 samples); β‐cubebene (Group IV, 8/52 samples) and by germacrene B and germacrene D (Group II, 6/52 samples). A special attention was brought to the quantification of the thermolabile components, germacrene A, germacrene B and germacrene C, as well as that of their rearranged compounds, β‐elemene, γ‐elemene and δ‐elemene. 13C‐NMR data of β‐cubebene have been provided.