Essential oil variability in Thymbra capitata (L.) Cav. growing wild in Southern Apulia (Italy)

Essential oils of Thymbra capitata (Thymus capitatus) collected from Southern Apulia (Italy) were analysed using gas chromatography and gas chromatography–mass spectrometry techniques, to check for chemical variability. The study showed that among the 75 components of the oils the most recurrent ones were thymol and carvacrol, which always constituted more than 50% of the oils, as well as γ-terpinene, borneol and p-cymene. Cluster analysis led to the identification of three chemotypes: thymol, carvacrol and thymol/carvacrol; this was presumably a crossbreed between the other two chemotypes. Principal component analysis showed the direct correlation among myrcene, α-terpinene and γ-terpinene; anti-correlation between thymol and carvacrol, and the inverse correlation between linalool and myrcene. Moreover, lower thymol concentrations were accompanied by an increase in myrcene, α-terpinene and γ-terpinene.     

Chemometric Tools to Highlight the Variability of the Chemical Composition and Yield of Lebanese Origanum syriacum L. Essential Oil

This study deals with the variation in the yield and composition of Lebanese Origanum syriacum L. essential oil (EO) according to harvesting time, drying methods used, and geographical location. Plant material was harvested twice a month all over 2013 and 2014 from Qartaba and Achkout located at high altitude and from Byblos at low altitude. EOs of the aerial parts were obtained by hydrodistillation. The highest yields were obtained at full flowering stage and slightly reduced after flowering. The GC/MS analysis revealed the presence of 50 components representing 90.49 – 99.82%, 88.79 – 100%, and 95.28 – 100% of the total oil extracted from plants harvested from Qartaba, Achkout, and Byblos, respectively. The major components in the oils were: carvacrol (2.1 – 79.8%), thymol (0.3 – 83.7%), p‐cymene (2.8 – 43.8%), thymoquinone (0.4 – 27.7%), γ‐terpinene (0.4 – 10.0%), octan‐3‐ol (0.3 – 4.9%), caryophyllene oxide (0.2 – 4.7%), oct‐1‐en‐3‐ol (0.3 – 3.7%), β‐caryophyllene (0.7 – 3.2%), cis‐sabinene hydrate (0.1 – 2.8%), terpinen‐4‐ol (0.1 – 2.8%), and α‐terpinene (0.2 – 2.2%). Independent components analysis (ICA) revealed that two groups were discriminated, reflecting compositional differences in the EOs profiles of the Lebanese oregano samples: O. syriacum grown in Qartaba and Achkout belongs to carvacrol chemotype, while O. syriacum grown in Byblos belongs to thymol chemotype. The flowering phase was the most productive period in terms of yield, bringing marked changes in the EO composition by increasing the amounts of carvacrol or thymol, and decreasing those of thymoquinone and p‐cymene.     

Variation of Essential Oil Content and Composition,Phenolics, and Yield Related Traits Using Different Pollination Systems in Populations of Thymus Species

The production of self-pollinated plants could be important for improving medicinal plants secondary metabolites. In this study, 11 Thymus populations from eight species were evaluated to determine the effect of self and open pollination on agro-morphological characteristics, total phenolic content (TPC), essential oil (EO) content, and EO components. Inbreeding led to some positive effects of above mentioned traits in most of the studied populations. Total phenolic content ranged from 7.07 to 52.69 mg tannic acid equivalents (TAE) g⁻¹ dry weight (DW) in open pollinated derived populations, while it varied from 1.2 to 55.03 mg TAE g⁻¹ DW in self-pollinated ones. Under open and self-pollination condition, the highest EO content was obtained in T. trautvetteri (3.37 %) and T. pubescens (1.96 %), respectively. Gas chromatography-mass spectrometry (GC/MS) identified 42 compounds including thymol, carvacrol, linalool, p-cymene, γ-terpinene, terpinen-4-ol, and α-terpineol as the main compounds. In most cases, selfed plants compared to open pollinated ones, revealed higher thymol content. T. daenensis-1 showed a significant increase in thymol content (from 25.22 % to 74.3 %) due to self-pollination. Moreover, self-pollination led to emergence of some new compounds. Carvacrol methyl ether was the constituents of Thymus EO that are being reported in self-pollinated populations. Finally, inbreeding in Thymus might be suggested as a useful tool to increase genetic homogeneity for the selection of superior plants for improving secondary metabolite.     

Chemical Polymorphism of Origanum compactum Grown in All Natural Habitats in Morocco

Origanum compactum L. (Lamiaceae) is one of the most important medicinal species in term of ethnobotany in Morocco. It is considered as a very threatened species as it is heavily exploited. Its domestication remains the most efficient way to safeguard it for future generations. For this purpose, wide evaluation of the existing variability in all over the Moroccan territory is required. The essential oils of 527 individual plants belonging to 88 populations collected from the whole distribution area of the species in Morocco were analyzed by GC/MS. The dominant constituents were carvacrol (0 – 96.3%), thymol (0 – 80.7%), p‐cymene (0.2 – 58.6%), γ‐terpinene (0 – 35.2%), carvacryl methyl ether (0 – 36.2%), and α‐terpineol (0 – 25.8%). While in the Middle Atlas region and the Central Morocco mainly carvacrol type samples were found, much higher chemotypic diversity was encountered within samples from the north part of Morocco (occidental and central Rif regions). The high chemical polymorphism of plants offers a wide range for selection of valuable chemotypes, as a part of breeding and domestication programs of this threatened species.     

High Diversity of Indigenous Populations of Dalmatian Sage (Salvia officinalis L.) in Essential‐Oil Composition

Essential oils of 25 indigenous populations of Dalmatian sage (Salvia officinalis L.) that represent nearly half of native distribution area of the species were analyzed. Plantlets collected from wild populations were grown in the same field under the same environmental conditions and then sampled for essential‐oil analysis. The yield of essential oil ranged from 1.93 to 3.70% with average of 2.83%. Among the 62 compounds detected, eight (cis‐thujone, camphor, trans‐thujone, 1,8‐cineole, β‐pinene, camphene, borneol, and bornyl acetate) formed 78.13–87.33% of essential oils of individual populations. Strong positive correlations were observed between camphor and β‐pinene, β‐pinene and borneol, as well as between borneol and bornyl acetate. The strongest negative correlation was detected between camphor and trans‐thujone. Principal component analysis (PCA) on the basis of eight main compounds showed that first main component separated populations with high thujone content, from those rich in camphor, while the second component separated populations rich in cis‐thujone from those rich in trans‐thujone. Cluster analysis (CA) led to the identification of three chemotypes of S. officinalis populations: cis‐thujone; trans‐tujone, and camphor/β‐pinene/borneol/bornyl acetate. We propose that differences in essential oils of 25 populations are mostly genetically controlled, since potential environmental factors were controlled in this study.     

Chemotype Diversity of Indigenous Dalmatian Sage (Salvia officinalis L.) Populations in Montenegro

To identify how many chemotypes of Salvia officinalis exist in Montenegro, the chemical composition of the essential oils of 12 wild‐growing populations was determined by GC‐FID and GC/MS analyses. Among the 40 identified constituents, the most abundant were cis‐thujone (16.98–40.35%), camphor (12.75–35.37%), 1,8‐cineol (6.40–12.06%), trans‐thujone (1.5–10.35%), camphene (2.26–9.97%), borneol (0.97–8.81%), viridiflorol (3.46–7.8%), limonene (1.8–6.47%), α‐pinene (1.59–5.46%), and α‐humulene (1.77–5.02%). The composition of the essential oils under study did not meet the ISO 9909 requirements, while the oils of populations P02–P04, P09, and P10 complied with the German Drug Codex. A few of the main essential‐oil constituents appeared to be highly intercorrelated. Strong positive correlations were observed between α‐pinene and camphene, camphene and camphor, as well as between cis‐thujone and trans‐thujone. Strong negative correlations were evidenced between cis‐thujone and α‐pinene, cis‐thujone and champhene, cis‐thujone and camphor, as well as between trans‐thujone and camphene. Multivariate analyses allowed the grouping of the populations into three distinct chemotypes, i.e., Chemotype A, rich in total thujones, Chemotype B, with intermediate contents of thujones, α‐pinene, camphene, and camphor and high borneol contents, and Chemotype C, rich in camphor, camphene, and α‐pinene. The chemotypes did not significantly differ in the total essential‐oil content and the cis/trans‐thujone ratio.     

Variation in Phytochemical,Morphological, and Ploidy Levels of Iranian Thymus Species

Thymus is one of the most important genera of the Lamiaceae family. This work was performed to assess inter and intra species variation, which is an indispensable prerequisite for the selection and the exploitation of the germplasm, using yield, secondary metabolites, and ploidy level criteria. Nineteen Iranian populations belonging to 11 Thymus species which includes T. vulgaris were used in this study. The results of cytological observations on the 19 populations revealed the three root-tip chromosome numbers of 2n=2x=30, 2n=4x=56 or 60 (diploid and tetraploid). This study also presents the results of a two-year field experiment that evaluates the agronomic and morphology of the 19 populations of Thymus spp. Cluster analysis grouped the populations into six groups and explained the relationships among ploidy levels, morphological traits, and essential oils (EOs). In general, diploid species belonged to the thymol chemotype, whilst carvacrol chemotype consistently dependent on the gene-dosage effect. Thymus migricus, T. daenensis-2, T. serpyllum, and T. trautvetteri populations with diverse thymol background were the best selection as the parents to improve thymol in a breeding program. Moreover, dry and fresh weight criteria can be used to improve EO content in thyme. Achieving this goal would be expected by crossing T. migricus and T. daenensis-2. Finally, providing relevant information on the ploidy level of Thymus species, with emphasis on morphology and EO components variations, may be recommended for the selection of populations or species to improve bioactive components as well as morphological traits in future breeding programs.     

Chemical and Olfactory Analysis of the Volatile Fraction of Ocimum gratissimum Concrete from Madagascar

The chemical composition of the volatile fraction of Ocimum gratissimum concrete (romba) from Madagascar has been determined for the first time by GC/MS and GC-FID. A methyl cinnamate chemotype has been determined for this material, along with a set of compounds typical in essential oils and extracts from plants of the Ocimum genus. Variability was mostly observed on terpenes and terpenoids components. GC-O-MS was also used for a sensory evaluation of this material performed by a master perfumer. The chemical composition of this O. gratissimum extract was then compared with literature data to assess subtle differences between chemotypes of the same species and other species of the same genus within natural variability. A mapping illustrates the occurrence of the cinnamate chemotype in Eastern Africa, India and now Madagascar, while other origins generally present eugenol, thymol, camphor, or linalool chemotypes.     

Essential oil variability of Thymus hyemalis growing wild in Southeastern Spain

Essential oils obtained by steam-distillation of individual samples of Thymus hyemalis were examined for variability in their volatile components by means of gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The thymol chemotype is widespread and is found in most of the vegetal formations where Thymus hyemalis is predominant and does not interact with other species. The carvacrol chemotype is found in isolated individual plants among those containing thymol. Although the chemotypes are usually mutually exclusive, the two phenols occasionally found with similar quantities in the same plant. The linalool chemotype has not previously been described for Thymus hyemalis. Other nonphenolic compounds (1,8-cineole, borneol, α-pinene) are present in low to medium percentages that reflect localized interactions with other species of thyme (Thymus vulgaris, Thymus baeticus) that sometimes produce hybridized or introgressive, morphologically distinguishable individuals.This chemical variability is analyzed by Principal Component Analysis (PCA) and Cluster Analysis (CA), a closely-related phenolic group of samples being revealed separated from less well represented non-phenolic chemotypes or mixed chemotypes. Multidimensional Scaling Analysis (MDS) based on percentage concentration was used to show the relationships between the most important components of the essential oil, the opposite orientation of vectors that represent phenolic compounds (and their precursors) and linalool, being of note. The data set presents positive correlation between camphor and altitude.     

Identification of the Chemotypes of Ocimum forskolei and Ocimum basilicum by NMR Spectroscopy

The chemotypes of Ocimum forskolei Benth and Ocimum basilicum L. growing wild in Oman have been established by ¹³C‐NMR analyses of the vegetative and floral oils of the plants. The chemotypes, estragole for O. forskolei and linalool for O. basilicum, suggested by ¹³C‐NMR fingerprinting were also confirmed by GC‐FID and GC/MS analyses. The oil of O. forskolei demonstrated better activities against bacteria and dermatophytes. The significance of the presence of estragole and linalool in the volatile oils of plants whose fragrances are traditionally inhaled, added to food, or rubbed on the skin are discussed.     

Chemotaxonomic Investigations of Peel and Petitgrain Essential Oils from 17 Citron Cultivars

Chemical compositions of essential oils from 17 citron cultivars were studied using GC and GC/MS. To the best of our knowledge, chemical compositions of peel and petitgrain oils from seven of them were reported for the first time. Combined analysis of peel and petitgrain essential oils led to the identification of 37 components (amounting to 98.2–99.9% of the total oil) and 42 components (97.0–99.9%), respectively. Statistical analysis was applied to identify possible relationships between citron cultivars. The levels of seven components, i.e., limonene, β‐pinene, γ‐terpinene, neral, geranial, nerol, and geraniol, indicated that the cultivars could be classified in four main chemotypes for peel and petitgrain oils. Chemotaxonomic investigations were carried out to establish relations between the morphological characteristics of citron cultivars and their corresponding oil compositions.     

Biomolecular Characterization of Wild Sicilian Oregano: Phytochemical Screening of Essential Oils and Extracts,and Evaluation of Their Antioxidant Activities

An extensive survey of wild Sicilian oregano was made. A total of 57 samples were collected from various sites, followed by taxonomic characterization from an agronomic perspective. Based on morphological and production characteristics obtained from the 57 samples, cluster analysis was used to divide the samples into homogeneous groups, to identify the best biotypes. All samples were analyzed for their phytochemical content, applying a cascade‐extraction protocol and hydrodistillation, to obtain the non volatile components and the essential oils, respectively. The extracts contained thirteen polyphenol derivatives, i.e., four flavanones, seven flavones, and two organic acids. Their qualitative and quantitative characterization was carried out by LC/MS analyses. The essential oils were characterized using a combination of GC‐FID and GC/MS analyses; a total of 81 components were identified. The major components of the oils were thymol, p‐cymene, and γ‐terpinene. Cluster analysis was carried out on both phytochemical profiles and resulted in the division of the oregano samples into different chemical groups. The antioxidant activity of the essential oils and extracts was investigated by the Folin? Ciocalteau (FC) colorimetric assay, by UV radiation‐induced peroxidation in liposomal membranes (UV‐IP test), and by determining the O ‐scavenging activity.     

Essential Oils of Myrtaceae Species Growing Wild in Tunisia: Chemical Variability and Antifungal Activity Against Biscogniauxia mediterranea,the Causative Agent of Charcoal Canker

The chemical composition of five Eucalyptus species and five Myrtus communis L. populations was investigated using GC/MS and GC‐FID. For Eucalyptus essential oils, 32 compounds, representing 88.56 – 96.83% of the total oil according to species, were identified. The main compounds were 1,8‐cineole, α‐pinene, p‐cymene, γ‐gurjunene, α‐aromadendrene, and β‐phellandrene. For Myrtle essential oils, 26 compounds, representing 93.13 – 98.91% of the total oil were identified. α‐Pinene, 1,8‐cineole, linalool, and myrtenyl acetate were found to be the major compounds. Principal component analysis (PCA) showed chemical differentiation between Eucalyptus species and between Myrtle populations. Biscogniauxia mediterranea, the causative agent of charcoal canker, was identified according to its morphological and molecular characteristics. Essential oils of the investigated Eucalyptus species and Myrtle populations were tested for their antifungal capacity against this fungus. The antifungal activity varied according to the essential oil composition. Biscogniauxia mediterranea exhibited powerful resistance to some essential oils including them of Eucalyptus lehmannii and Eucalyptus sideroxylon but it was very sensitive to Eucalyptus camaldulensis oil (IC₅₀ = 3.83 mg/ml) and M. communis oil from Zaghouan (IC₅₀ = 1 mg/ml). This sensitivity was found to be correlated to some essential oil compounds such as p‐cymene, carvacrol, cuminaldehyde, and linalool.     

Yield,chemical composition,and bioactivity of essential oils from 12 species of Eucalyptus on Aedes aegypti larvae

The insecticidal activity of essential oils from 12 species of Eucalyptus (Myrtaceae) was evaluated on larvae of Aedes aegypti (L.) (Diptera: Culicidae), the most important vector of dengue and yellow fever in the Americas. Oils were obtained by hydrodistillation and their chemical composition was determined by gas chromatography coupled to mass spectrometry; yields ranged from 0.2 to 2.5%. Essential oils were mainly composed of 1,8‐cineole, α‐pinene, α‐phellandrene, β‐phellandrene, γ‐terpinene, 4‐terpineol, α‐terpineol, p‐cymene, and spathulenol. Larvicidal effects were tested on susceptible third or fourth stage Ae. aegypti larvae, determining median lethal concentration (LC₅₀) and median effective concentration (EC₅₀). Essential oils from Eucalyptus dunnii (Maiden), Eucalyptus gunnii (Hook), Eucalyptus tereticornis (Smith), Eucalyptus camaldulensis (Dehn), and Eucalyptus saligna (Smith) showed the best larvicidal activities with LC₅₀ values of 25.2, 21.1, 22.1, 26.8, and 22.2, respectively. No significant differences were observed between LC₅₀ and EC₅₀ values of the same oil. Regression analysis revealed a significant relationship between total essential oil yields and 1,8‐cineole concentration. Significant relationships were also revealed between larval mortality and the concentration of 1,8‐cineole and p‐cymene. This indicated that Eucalyptus species with high oil yields have higher 1,8‐cineole concentrations and lower p‐cymene concentrations and have less effect on Ae. aegypti. Our results suggest the potential of controlled crossing methods to obtain Eucalyptus trees with chemical profiles having enhanced activity against this mosquito.     

Variation in volatile leaf oils of five Eucalyptus species harvested from Jbel Abderrahman arboreta (Tunisia)

Hydrodistillation of the dried leaves of five species of the genus Eucalyptus L' Hér ., viz., E. dundasii Maiden , E. globulus Labill ., E. kitsoniana Maiden , E. leucoxylon F. Muell ., and E. populifolia Hook ., harvested from Jbel Abderrahman arboreta (region of Nabeul, northeast of Tunisia) in April 2006, afforded essential oils in yields varying from 0.9±0.3 to 3.8±0.6%, dependent on the species. E. globulus and E. Kitsoniana provided the highest and the lowest percentage of essential oil amongst the species examined, respectively. Analysis by GC (RI) and GC/MS allowed the identification of 127 compounds, representing 93.8 to 98.7% of the total oil composition. The contents of the different samples varied according to the species. The main components were 1,8‐cineole ( 2 ; 4.7–59.2%), followed by α‐pinene ( 1 ; 1.9–23.6%), trans‐pinocarveol ( 6 ; 3.5–21.6%), globulol ( 8 ; 4.3–12.8%), p‐cymene ( 3 ; 0.5–6.7%), α‐terpineol (1.5–4.5%), borneol (0.2–4.4%), pinocarvone (1.1–3.8%), aromadendrene (1.4–3.4%), isospathulenol (0.0–1.9%), fenchol ( 4 ; 0.1–2.5%), limonene (1.0–2.4%), epiglobulol (0.6–2.1%), viridiflorol ( 9 ; 0.8–1.8%), and spathulenol (0.1–1.6%). E. leucoxylon was the richest species in 2 . Principal component analysis (PCA) and hierarchical cluster analysis (HCA) separated the five Eucalyptus leaf essential oils into four groups, each constituting a chemotype.     

Larvicidal Activity of Essential Oils of Five Apiaceae Taxa and Some of Their Main Constituents Against Culex quinquefasciatus

Apiaceae are aromatic herbs producing essential oils which are used on an industrial scale for various purposes. Notably, Apiaceae essential oils may replace synthetic insecticides keeping most of their efficacy and avoiding environmental pollution and human poisoning. In the present work, we explored the insecticidal potential of the essential oils from five Apiaceae taxa, namely Sison amomum, Echinophora spinosa, Heracleum sphondylium subsp. sphondylium, Heracleum sphondylium subsp. ternatum, and Trachyspemum ammi, as well as their major constituents (sabinene, p‐cymene, terpinolene, myristicin, and thymol), against the filariasis vector Culex quinquefasciatus. For the purpose, the essential oils were obtained by hydrodistillation and their composition was achieved by gas chromatography/mass spectrometry (GC/MS). Their acute toxicity on third instar larvae of C. quinquefasciatus was determined. The two most active essential oils were those from T. ammi fruits and E. spinosa roots, showing LC₅₀ below 20 μl/l and LD₉₀ below 50 μl/l. These oils were dominated by the monoterpene phenol thymol and the phenylpropanoid myristicin, respectively, which showed the strongest larvicidal activity (LC₅₀ of 15.1 and 16.3 μl/l, respectively) among the pure compounds tested. These results showed that Apiaceae may be useful as source of larvicidal compounds to be used for the development of cheap, effective and eco‐friendly insecticidal formulations.     

Genetic Diversity and Chemical Polymorphism of Some Thymus Species

To ascertain whether there are chemical and genetic relationships among some Thymus species and also to determine correlation between these two sets of data, the essential‐oil composition and genetic variability of six populations of Thymus including: T. daenensis ?elak. (two populations), T. fallax Fisch . & C.A.Mey ., T. fedtschenkoi Ronniger , T. migricus Klokov & Des .‐Shost ., and T. vulgaris L. were analyzed by GC and GC/MS, and also by randomly amplified polymorphic DNA (RAPD). Thus, 27 individuals were analyzed using 16 RAPD primers, which generated 264 polymorphic scorable bands and volatiles isolated by distillation extraction were subjected to GC and GC/MS analyses. The yields of oils ranged from 2.1 to 3.8% (v/w), and 34 components were identified, amounting to a total percentage of 97.8–99.9%. RAPD Markers allowed a perfect distinction between the different species based on their distinctive genetic background. However, they did not show identical clustering with the volatile‐oil profiles.     

Influence of Morphological Variability and Habitat on the Chemical Composition of Essential Oils of an Algerian Endemic Origanum Species (Origanum floribundum Munby)

The genus Origanum L. (Lamiaceae) enjoys a socioeconomic interest and constitutes one of the most popular spices. In the literature, the study of this taxon is limited mainly to the chemical composition, antimicrobial, antifungal, and antioxidant activities of the essential oils. In Algeria, few works have been done in this area, including the endemic and rare species: Origanum floribundum Munby . In this study, our contribution highlights the influence of the ecological parameters and of the variation of morphological traits on the chemical composition and the antioxidant activity of the essential oils of six populations. The major oils constituents are carvacrol, γ‐terpinene, and p‐cymene with carvacrol predominance (31.8 – 60.8%) in over five populations (MS1 – MS4 and MS6). However, the population of Ain Terraeur (MS5) of which individuals present a foliar polymorphism, distinguishes itself by p‐cymene predominance (42.6%). This would denote a new chemotype and/or variety which seem well differentiated on the dendrogram of the Ascending Hierarchical Classification (A.H.C) and its foliar morphology. The antioxidant activity of the six samples evaluated by the scavenging activity of free radicals DPPH^? and ABTS^?+ showed a potent efficiency for the sample with foliar polymorphism population (IC₅₀ = 51.6 ± 0.31 and 12.71 ± 0.37 μg/ml, respectively).     

Essential‐Oil Composition of Daucus carota ssp. major (Pastinocello Carrot) and Nine Different Commercial Varieties of Daucus carota ssp. sativus Fruits

The chemical composition of the essential oils obtained by hydrodistillation from the pastinocello carrot, Daucus carota ssp. major (Vis.) Arcang . (flowers and achenes), and from nine different commercial varieties of D. carota L. ssp. sativus (achenes) was investigated by GC/MS analyses. Selective breeding over centuries of a naturally occurring subspecies of the wild carrot, D. carota L. ssp. sativus, has produced the common garden vegetable with reduced bitterness, increased sweetness, and minimized woody core. On the other hand, the cultivation of the pastinocello carrot has been abandoned, even if, recently, there has been renewed interest in the development of this species, which risks genetic erosion. The cultivated carrot (D. carota ssp. sativus) and the pastinocello carrot (D. carota ssp. major) were classified as different subspecies of the same species. This close relationship between the two subspecies urged us to compare the chemical composition of their essential oils, to evaluate the differences. The main essential‐oil constituents isolated from the pastinocello fruits were geranyl acetate (34.2%), α‐pinene (12.9%), geraniol (6.9%), myrcene (4.7%), epi‐α‐bisabolol (4.5%), sabinene (3.3%), and limonene (3.0%). The fruit essential oils of the nine commercial varieties of D. carota ssp. sativus were very different from that of pastinocello, as also confirmed by multivariate statistical analyses.     

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.