Isabelle Bombarda

Chemometric analysis of French lavender and lavandin essential oils by near infrared spectroscopy

Abstract Chemometric treatments of near infrared (NIR) spectra were used firstly to understand data structure by principal component analysis (PCA), to discriminate, by partial least squares-discriminant analysis (PLS-DA) regression, French lavender and lavandin essential oils (EOs) samples ( n xa0=xa0160) and the seven varieties (Abrial, Fine, Grosso, Maillette, Matherone, Sumian and Super) and to quantify the main compounds such as linalyl acetate, linalool, eucalyptol and camphor by PLS regression models. The study was carried out over three crop years (2012–2014) to take seasonal variations into account. French lavender and lavandin EOs and their varieties were well classified (100% for lavender/lavandin EOs and between 96 and 100% for varieties) by PLS-DA regression models. The calibration models obtained by PLS regression for the determination of the main compound contents revealed good correlation (≥0.97) between the predicted and reference values. In the case of major compounds including linalyl acetate and linalool, the relative error of prediction (REP) is close to 2.5%. Partial least squares regression vectors allowed us to identify lavandulyl acetate, eucalyptol, linalool, camphor, trans -β-ocimene, β-caryophyllene and linalyl acetate as metabolomic indicators of Fine, Maillette, Matherone, Abrial, Grosso, Super and Sumian varieties respectively. The use of NIR spectra allowed for an improvement in French lavender and lavandin EOs characterization, quality control and traceability.

Analysis of the major chiral compounds of Artemisia herba-alba essential oils (EOs) using reconstructed vibrational circular dichroism (VCD) spectra: En route to a VCD chiral signature of EOs.

An unprecedented methodology was developed to simultaneously assign the relative percentages of the major chiral compounds and their prevailing enantiomeric form in crude essential oils (EOs). In a first step the infrared (IR) and vibrational circular dichroism (VCD) spectra of the crude essential oils were recorded and in a second step they were modelized as a linear weighted combination of the IR and VCD spectra of the individual spectra of pure enantiomer of the major chiral compounds present in the EOs. The VCD spectra of enantiomer of known enantiomeric excess shall be recorded if they are not yet available in a library of VCD spectra. For IR, the spectra of pure enantiomer or racemic mixture can be used. The full spectra modelizations were performed using a well known and powerful mathematical model (least square estimation: LSE) which resulted in a weighting of each contributing compound. For VCD modelization, the absolute value of each weighting represented the percentage of the associate compound while the attached sign addressed the correctness of the enantiomeric form used to build the model. As an example, a model built with the non-prevailing enantiomer will show a negative sign of the weighting value. For IR spectra modelization, the absolute value of each weighting represented the percentage of the compounds without of course accounting for the chirality of the prevailing enantiomers. Comparison of the weighting values issuing from IR and VCD spectra modelizations is a valuable source of information: if they are identical, the EOs are composed of nearly pure enantiomers, if they are different the chiral compounds of the EOs are not in an optically pure form. The method was applied on four samples of essential oil of Artemisia herba-alba in which the three major compounds namely (-)-α-thujone, (+)-β-thujone and (-)-camphor were found in different proportions as determined by GC-MS and chiral HPLC using polarimetric detector. In order to validate the methodology, the modelization of the VCD spectra was performed on purpose using the individual VCD spectra of (-)-α-thujone, (+)-β-thujone and (+)-camphor instead of (-)-camphor. During this work, the absolute configurations of (-)-α-thujone and (+)-β-thujone were confirmed by comparison of experimental and calculated VCD spectra as being (1S,4R,5R) and (1S,4S,5R) respectively.

Isolation of the major chiral compounds from Bubonium graveolens essential oil by HPLC and absolute configuration determination by VCD.

The chirality issues in the essential oils (EOs) of leaves and flowers from Bubonium graveolens were addressed by chiral high-performance liquid chromatography (HPLC) with polarimetric detection and vibrational circular dichroism (VCD). The chemical compositions of the crude oils of three samples were established by gas chromatography / mass spectrometry (GC/MS). The well-known cis-chrysanthenyl acetate (1), oxocyclonerolidol (2), and the recently disclosed cis-acetyloxychrysanthenyl acetate (3), the three major chiral compounds, were isolated by preparative HPLC. The naturally occurring oxocycloneroledol (2), mostly found in the leaf oil (49.4-55.6%), presents a (+) sign in the mobile phase during HPLC on a chiral stationary phase (CSP) with a Jasco polarimetric detection. The naturally occurring cis-chrysanthenyl acetate (1) and cis-acetyloxychrysanthenyl acetate (3), mostly found in the flower EO (35.9-74.9% and 10.0-34.3%, respectively), both present a (-) sign. HPLC on a CSP with polarimetric detection is an unprecedented approach to readily differentiate the flower and leaf EOs according to their chiral signature. The comparison of the experimental and calculated VCD spectra of pure isolated 1, 2, and 3 provided their absolute configuration as being (1S,5R,6S)-(-)-2,7,7-trimethylbicyclo[3.1.1]hept-2-en-6-yl acetate 1, (2R,6R)-(+)-6-ethenyl-2,6-dimethyl-2-(4-methylpent-3-en-1-yl)dihydro-2H-pyran-3(4H)-one) 2 and (1S,5R,6R,7S)-(-)-7-(acetyloxy)-2,6-dimethylbicyclo[3.1.1]hept-2-en-6-yl]methyl acetate 3. Compounds 1, 2, and 3 were already known in B. graveolens but this is the first report of the absolute configuration of (+)-2 and (-)-3. The VCD chiral signatures of the crude oils were also recorded.

Artemisia arborescens Essential Oil Composition, Enantiomeric Distribution, and Antimicrobial Activity from Different Wild Populations from the Mediterranean Area.

Aerial parts of Artemisia arborescens were collected from different sites of the Mediterranean area (southwestern Algeria and southern Italy) and the chemical composition of their essential oil (EO) extracted by hydrodistillation was studied by both gas chromatography (GC) equipped with an enantioselective capillary column and GC/mass spectrometry (GC/MS). The EOs obtained were tested against several Listeria monocytogenes strains. Using GC and GC/MS, 41 compounds were identified, accounting for 96.0 – 98.8% of the total EO. All EOs showed a similar terpene profile, which was rich in chamazulene, β‐thujone, and camphor. However, the concentration of such compounds varied among the EOs. A. arborescens EO inhibited up to 83.3% of the L. monocytogenes strains, but the inhibitory spectrum varied among the EOs, with those from Algeria showing a higher inhibition degree than the Italian EOs. Such effect likely depended on the ketone (β‐thujone + camphor) content of the EO. The differences in the EO composition support the hypothesis that A. arborescens has at least two different chemotypes: a β‐thujone and a chamazulene type. The EO inhibitory spectrum indicates the A. arborescens EO as a valuable option in the control of the food‐borne pathogens.

New chemotype of essential oil of Achillea santolina L. collected from different regions of Algeria

Chemical composition of essential oil (EO) obtained by hydrodistillation of the aerial parts of Achillea santolina L. was analysed using GC and GC–MS. Especially, this study involved a large scale investigation, using different regions in which, five flowering wild growing populations collected from the high plateau of Algeria were engaged. Unlike previous reports, the current investigation showed very high EO yields for this plant (up to 1.7% w/w “dw”). The main result of the current study was the occurrence of a new chemotype rich in camphor (39.54–67.86%) and 1,8-cineole (7.14–8.57%).

Variability of composition and effects of essential oils from Rhanterium adpressum Coss. & Durieu against mycotoxinogenic Fusarium strains

The antifungal potency of the essential oils of Rhanterium adpressum was evaluated against four mycotoxigenic strains of the genus Fusarium. The essential oils were obtained, separately, by hydro-distillation of the aerial parts of R. adpressum (leaves and flowers). The parts were collected during the period of bloom (3xa0months) for 3xa0years. The GC–MS analysis revealed thirty-six compounds for the essential oils, divided into four classes of chemical compounds, with variable percentages according to the month of extraction. The monoterpene hydrocarbons form the main class in these oils. On the other hand, the highest percentages of the oxygenated compounds are observed in the samples collected during the month of May. The direct contact method was used to evaluate the antifungal activity of the essential oils. The activity can be attributed to their relatively high composition of oxygenated monoterpenes. Flowers extract showed strong inhibitory activity, with very interesting concentrations of IC50 and MIC for both tests on solid and liquid medium. The effect of these oils on the production of type B trichothecenes (TCTBs) was evaluated, showing a significant inhibitory effect on TCTBs production, for both extracts (leaves and flowers). The rates of inhibition were 66–97 and 76–100% of FX, 3-ADON and 15-ADON, respectively. The inhibition of fungal biomass and the production of TCTBs depended on the used concentration of the essential oils. These results suggest that the essential oils from R. adpressum are able to control the growth of the tested strains and their subsequent production of TCTB mycotoxins.

Antibacterial activity against methicillin-resistant Staphylococcus aureus of five essential oils from Algerian medicinal plants (Lamiaceae)

Abstract The susceptibility of two methicillin-resistant Staphylococcus Aureus (MRSA) and one methicillin-sensitive Staphylococcus Aureus (MSSA) to essential oils (EOs) extracted from five Algerian medicinal plants (Lamiaceae) was evaluated. Thymus fontanesii and Thymus numidicus EOs revealed a carvacrol chemical profile (62.7 and 46.8%, respectively) whereas Origanum glandulosum EO was characterized by high contents of carvacrol and thymol. Mentha pulegium was characterized by a high content of pulegone (74.8%) never put in evidence. The major components of Lavandula stoechas L. were fenchone (48.0%) and camphor (21.1%). Antibacterial activities against MRSA and MSSA were evaluated by disk diffusion method and microdilution broth assay. This is the first report on the antibacterial activity against MRSA for EOs from the species T. fontanesii and T. numidicus and for M. pulegium from Algeria. EOs were found to be strongly bactericidal (MIC from 0.3 μL/mL to 4.7 μL/mL) which suggests an additional option to treat MRSA infections.

Chemical composition, antioxidative, antimicrobial and anti-cancer activities of Asteriscus graveolens (Forssk) essential oil

This work is devoted to the study of the chemical composition and the evaluation of the biological activities of essential oils (EOs) extracted from the flowers of Asteriscus graveolens Forssk. plant. The EO sample was obtained by hydrodistillation and the chemical composition analysis was performed using GC and GC/MS. The major chemical components characterizing the EO were cis-chrysanthenyl acetate (44.30%) and cis-8-acetoxychrysanthenyl acetate (33.70%). Antioxidant activity was determined using DPPH and Phosphomolybdenum tests. Although the EO presented a weak scavenging activity (420.16xa0mg/mL), it exhibited good reducing power using the Phosphomolybdenum assay (0.28xa0AAEC/mg). The most important antibacterial activity was noted for Bacillus cereus. The oil revealed a remarkable activity against the nine fungi species tested with percentage inhibition up to 94.12% for Fusarium culmorum (BTCR). More important, this work investigated for the first time the anticancer effect of this EO on two types of cancer cell lines (human liver carcinoma and Rat pheochromocytoma cell lines). The EO showed a high anticancer activity against both tumor cell lines comparing to the positive control.

Essential oils composition of different Achillea santolina L. plant parts growing in Algeria

The essential oils (EOs) of leaves, flowers and stems of Achillea santolina L. (Asteraceae) collected at complete flowering stage from Southwest of Algeria, were isolated by hydrodistillation and subsequently analyzed by means of GC and GC/MS. Quantitative and qualitative differences in chemical compositions between the studied parts of this plant were observed. The EOs were rich in oxygenated monoterpenes (65.91–79.94%). The major constituents in the flowers, leaves and stems were: camphor (68.12, 65.17, 55.72%), 1,8-cineole (8.22, 4.77, 0.7%) and α-terpineol (2.84, 5.35, 2.76%). The highest EO yields were obtained for the leaves and the flowers (0.59 and 0.49% “v/w”, respectively), whereas, the stems were characterized by very weak yield value (0.05%).

NIR spectroscopy for the quality control of Moringa oleifera (Lam.) leaf powders: Prediction of minerals, protein and moisture contents

A rapid methodology was developed to simultaneously predict water content and activity values (aw) of Moringa oleifera leaf powders (MOLP) using near infrared (NIR) signatures and experimental sorption isotherms. NIR spectra of MOLP samples (nu202f=u202f181) were recorded. A Partial Least Square Regression model (PLS2) was obtained with low standard errors of prediction (SEP of 1.8% and 0.07 for water content and aw respectively). Experimental sorption isotherms obtained at 20, 30 and 40u202f°C showed similar profiles. This result is particularly important to use MOLP in food industry. In fact, a temperature variation of the drying process will not affect their available water content (self-life). Nutrient contents based on protein and selected minerals (Ca, Fe, K) were also predicted from PLS1 models. Protein contents were well predicted (SEP of 2.3%). This methodology allowed for an improvement in MOLP safety, quality control and traceability.