Smart IM-MS and NMR study of natural diastereomers: the study case of the essential oil from Senecio transiens.

Unambiguous identification of the components of a natural mixture remains a challenging and meticulous issue. Usually, different analytical techniques and laborious separation protocols are employed; nevertheless, in some cases, delicate and equivocal problems are hardly addressed by traditional methods. In this context, an original methodology for the analysis of natural samples consisting of recent mass spectrometry methods based on ion mobility (MS-IM) is proposed. As an example, a polar fraction obtained by the essential oil prepared from Senecio transiens, an endemic plant harvested on the Corsica Island, was selected for this study to show how IM-MS-based methods easily provide very useful insights suggesting the presence of two diastereomers. To unambiguously confirm this hypothesis and verify reliability of the IM-MS results, the purified compounds were further analysed by means of nuclear magnetic resonance (NMR) methodologies, allowing the structural elucidation and the identification of two new natural compounds, diastereomers of 4-acetoxy-5,9-dimethyl-3-(2-methylpropenyl)-2-oxabicyclo[4.4.0] dec-9-ene, reported here for the first time.

Direct Identification of α-Bisabolol Enantiomers in an Essential Oil Using a Combined Ion Mobility-Mass Spectrometry/Quantum Chemistry Approach.

Enantiomer-specific identification of chiral molecules in natural extracts is a challenging task, as many routine analytical techniques fail to provide selectivity in multicomponent mixtures. Here we describe an alternative approach, based on the combination of ion mobility-mass spectrometry (IM-MS) and quantum chemistry (QM), for the direct enantiomers differentiation in crude essential oils. The identification of α-bisabolol enantiomers contained in the raw essential oil (EO) from the Corsican Xanthium italicum fruits is reported as a proof-of-concept. Accordingly, IM-MS experiments performed in Ag+-doped methanol revealed the presence of both (+)- and (-)-α-bisabolol in the EO, while molecular simulations provided the structures of the two α-bisabolol enantiomer silver(I) adducts.

Chemical Composition of Essential Oils of Xanthium spinosum L., an Invasive Species of Corsica.

Xanthium spinosum L. is a highly invasive plant originated from South America throughout the world as well as in Corsica Island. The chemical composition of X. spinosum essential oils from 25 Corsican locations was investigated using GC-FID and GC/MS. Seventy-four components, which accounted for 96.2% of the total amount, were reported for the first time in the essential oil from aerial parts. The main compounds were eudesma-4(14),7-dien-1ß-ol (61; 21.3%), germacrene D (36; 8.8%) and cadalene (60; 8.7%). Comparison with the literature highlighted the originality of the Corsican essential oil and eudesma-4(14),7-dien-1ß-ol could be used as taxonomical marker to the systematics of the Xanthium genus. The essential oils obtained from separate organs and during the plant vegetative cycle were also studied to gain more knowledge about the correlations between the volatile production and the phenological states of this weed. The production of oxygenated sesquiterpenes was predominant during the plant-flowering process. The study focuses on direct correlation between the chemical composition of individual 25 oil samples and the morphological differences of the plant. Our results have gained more knowledge about the secondary metabolite production that occurs during the plant life, they could be interesting in order to manage the dispersal of X. spinosum.

Essential-oil composition and chemical variability of Senecio vulgaris L. from Corsica.

The chemical composition of the essential oils isolated from the aerial parts of Senecio vulgaris plants collected in 30 Corsican localities was characterized using GC-FID and GC/MS analyses. Altogether, 54 components, which accounted for 95.2% of the total oil composition, were identified in the 30 essential-oil samples. The main compounds were α-humulene (1; 57.3%), (E)-ß-caryophyllene (2; 5.6%), terpinolene (3; 5.3%), ar-curcumene (4; 4.3%), and geranyl linalool (5; 3.4%). The chemical composition of the essential oils obtained from separate organs and during the complete vegetative cycle of the plants were also studied, to gain more knowledge about the plant ecology. The production of monoterpene hydrocarbons, especially terpinolene, seems to be implicated in the plant-flowering process and, indirectly, in the dispersal of this weed species. Comparison of the present results with the literature highlighted the originality of the Corsican S. vulgaris essential oils and indicated that α-humulene might be used as taxonomical marker for the future classification of the Senecio genus. A study of the chemical variability of the 30 S. vulgaris essential oils using statistical analysis allowed the discrimination of two main clusters according to the soil nature of the sample locations. These results confirmed that there is a relation between the soil nature, the chemical composition of the essential oils, and morphological plant characteristics. Moreover, they are of interest for commercial producers of essential oil in selecting the most appropriate plants.

Chemical variability and antioxidant activity of Limbarda crithmoides L. essential oil from Corsica.

The chemical compositions of 25 Corsican Limbarda crithmoides ssp. longifolia essential oils were investigated for the first time using GC-FID, GC/MS, and NMR analyses. Altogether, 65 compounds were identified, accounting for 90.0-99.3% of the total oil compositions. The main components were p-cymene (1; 15.1-34.6%), 3-methoxy-p-cymenene (4; 11.8-28.5%), 2,5-dimethoxy-p-cymenene (5; 5.9-16.4%), thymol methyl ether (6; 1.3-14.9%), α-phellandrene (2; 0.9-11.9%), and α-pinene (3; 0.2-13.4%). The chemical variability of the Corsican oil samples was studied using multivariate statistical analysis, which allowed the discrimination of two main clusters. A direct correlation between the water salinities of the plant locations and the chemical compositions of the L. crithmoides essential oils was evidenced. Indeed, essential oils rich in 1 (30.4-34.6%) were found in samples growing in the wetlands of the southern oriental coast, which exhibit high salinity levels (24.4±0.2-33.9±0.2 ppt), and essential oils with lower contents of 1 (15.1-27.3%) were isolated form samples growing in the wetlands of northern Corsica, which exhibit lower salinity levels (10.90±0.20-15.47±0.15 ppt). The antioxidant potential of L. crithmoides essential oil was also investigated, by assessing the DPPH(.) - and ABTS(.+) -scavenging activities and the reducing power of ferric ions, and was found to be interesting. Moreover, using bioassay-guided fractionation of the essential oil, a higher antioxidant activity was obtained for the oxygenated fraction and both ester and alcohol subfractions.