Variation in Volatile Leaf Oils of Twelve Eucalyptus Species Harvested from Hajeb Layoun Arboreta (Tunisia)

Hydrodistillation of the dried leaves of twelve species of the genus Eucalyptus L' Hér ., i.e., E. brockwayi C. A. Gardn ., E. gracilis F. Muell ., E. gillii Maiden , E. largiflorens F. Muell ., E. loxophleba Benth ., E. occidentalis Endl ., E. oldfieldii F. Muell ., E. salmonophloia F. Muell ., E. sargentii Maiden , E. stricklandii Maiden , E. torquata Luehm ., and E. woodwardii Maiden , harvested from Hajeb Layoun arboreta (region of Kairouan, central Tunisia) in January 2005, afforded essential oils in yields varying from 0.5±0.1 to 5.7±0.5%, dependent on the species. E. sargentii and E. brockwayi provided the highest and the lowest percentage of essential oil amongst all the species examined, respectively. Analysis by GC (RI) and GC/MS allowed the identification of 133 components, representing 92.9–98.8% of the total oil. The contents of the different samples varied according to the species. The main components were 1,8‐cineole, terpinen‐4‐ol, α‐pinene ( 2 ), p‐cymene, aromadendrene ( 1 ), globulol ( 5 ), trans‐pinocarveol ( 6 ), spathulenol ( 7 ), β‐eudesmol, torquatone ( 3 ), and 4‐methylpentan‐2‐yl acetate ( 8 ). The principal component analysis and the hierarchical clustering indicated that the volatile leaf oil composition of the twelve Eucalyptus species could be clearly differentiated.     

Variation in Volatile Leaf Oils of Eleven Eucalyptus Species Harvested from Korbous Arboreta (Tunisia)

Hydrodistillation of the dried leaves of eleven species of the genus Eucalyptus L 'Hér ., i.e., E. astringens Maiden , E. camaldulensis Dehnh ., E. diversifolia Bonpl ., E. falcata Turcz ., E. ficifolia F. Muell ., E. gomphocephala DC., E. lehmannii (Schauer ) Benth ., E. maculata Hook ., E. platypus Hook ., E. polyanthemos Schauer, and E. rudis Endl ., harvested from Korbous arboreta (region of Nabeul, northeast of Tunisia) in April 2006, afforded essential oils in yields varying from 0.1±0.1 to 3.8±0.1%, dependent on the species. E. astringens and E. ficifolia showed the highest and the lowest mean percentage of essential oil amongst all the species examined, respectively. Analysis by GC (RI) and GC/MS allowed the identification of 138 components, representing 74.0 to 99.1% of the total oil. The contents of the different samples varied according to the species. The main components were 1,8‐cineole, followed by trans‐pinocarveol ( 1 ), spathulenol ( 2 ), α‐pinene, p‐cymene, (E,E)‐farnesol, cryptone, globulol ( 3 ), β‐phellandrene, α‐terpineol, viridiflorol, and α‐eudesmol. The principal‐component and the hierarchical‐cluster analyses separated the eleven Eucalyptus leaf essential oils into seven groups, each constituting a chemotype.     

Variation in Volatile Leaf Oils of 13 Eucalyptus Species Harvested from Souinet Arboreta (Tunisia)

Hydrodistillation of the dried leaves of 13 species of the genus Eucalyptus L' Hér ., viz., E. bicostata Maiden, Blakely & Simmonds , E. cinerea F. Muell . ex Benth ., E. exerta F. Muell ., E. gigantea Hook . f ., E. gunnii Hook . f ., E. macarthurii Deane & Maiden ., E. macrorrhyncha F. Muell ., E. maidenii F. Muell ., E. odorata Behr ., E. pauciflora Sieber ex Sprengel , E. sideroxylon A. Cunn . ex Woolls , E. tereticornis Sm ., and E. viminalis Labill ., harvested from Souinet arboreta (region of Ain Draaham, north of Tunisia) in June 2006, afforded essential oils in yields varying from 0.5±0.2 to 3.9±0.4%, dependent on the species. E. cinerea and E. exerta provided the highest and the lowest percentage of essential oil amongst all the species examined, respectively. Analysis by GC (RI) and GC/MS allowed the identification of 142 components, representing 81.5 to 98.9% of the total oil. The contents of the different samples varied according to the species. The main components were 1,8‐cineole ( 1 ), followed by cryptone, spathulenol ( 4 ), p‐cymene ( 2 ), viridiflorol ( 6 ), globulol ( 7 ), β‐eudesmol, α‐terpineol ( 5 ), limonene ( 8 ), D ‐piperitone, α‐pinene ( 3 ), cuminal, and γ‐eudesmol. The principal component and the hierarchical cluster analyses separated the 13 Eucalyptus leaf essential oils into three groups, each constituting a chemotype.     

Chemical Characterization of Five Tunisian Eucalyptus Essential Oils Species

Hydrodistillation of the dried leaves of five Eucalyptus species, E. alba Reinw. ex Blume , E. citriodora Hook ., E. paniculata Sm. , harvested from Choucha arboreta (region of Sejnane, northwest of Tunisia), E. pimpiniana Maiden from Mjez Elbab arboreta (north east of Tunisia) and E. bicolor A.Cunn ex Hook from Sidi Smail arboreta (center of Tunisia), in March 2017, afforded essential oils in yields varying from 1.3±0.2 to 6.0±0.9 % according to the species. E. citriodora provided the highest mean percentage of essential oil amongst all the species. Analysis by GC (RI) and GC/MS allowed the identification of 138 components representing 84.6–98.7 % of the total oil. The content of the different samples varied according to the species. The main components were citronellol, followed by 1,8‐cineole, α‐pinene, τ‐cadinol, 7‐epi‐α‐eudesmol, trans‐pinocarveol, spathulenol, aromadendrene, γ‐cadinene and δ‐cadinene. The principal components and the hierarchical cluster analyses separated the five leaf essential oils into three groups, each group constituted a chemotype.     

Chemodiversity and α-Glucosidase Activity of Eucalyptus Species from Northwestern Himalaya,India

The aim of current work was to determine essential oils (EOs) composition from three Eucalyptus species, including E. citriodora, E. camaldulensis and E. globulus and assess their α-glucosidase inhibitory activity. The EOs were collected using the hydrodistillation technique and characterized by GC/MS, GC-FID and NMR. The isolated EOs from leaves parts of Eucalyptus species varied from 0.56 to 1.0 % on fresh weight basis. The content of the EOs was distinct according to the species. The most abundant metabolites were identified as citronellal (0–83.0 %), 1,8-cineole (0.2–44.8 %), spathulenol (0.4–16.1 %) α-pinene (0.4–15.9 %), p-cymene (3.7–11.9 %), citronellol (0–8.6 %), β-eudesmol (5.3–8.6 %) and β-pinene (0–7.1 %). The EOs obtained from targeted samples exhibited strong α-glucosidase inhibitory activity. These results are encouraging and underline that the EOs of Eucalyptus species may be a promising alternative source of natural antidiabetic.     

Essential Oil from Blackcurrant Buds as Chemotaxonomy Marker and Antimicrobial Agent

Dormant buds are recognized as valuable side product of the blackcurrant cultivation. Four blackcurrant varieties cultivated in Serbia, i.e., Ben Sarek, Ometa, Ben Lomond, and Ben Nevis, were evaluated for the content, chemical composition, and antimicrobial activity of their bud essential oils. The oil yields of buds harvested during two different growth periods ranged from 1.2–2.0%, and the variety Ometa had the highest yield among the tested varieties. GC‐FID and GC/MS analysis of the oils allowed the identification of eight main components, i.e., α‐pinene (1.6–5.4%), sabinene (1.9–38.4%), δ‐car‐3‐ene (13.0–50.7%), β‐phellandrene (2.9–18.0%), terpinolene (6.6–11.9%), terpinen‐4‐ol (0.9–6.6%), β‐caryophyllene (3.8–10.4%), and α‐humulene (0.2–4.1%). In addition, the similarity degree of the essential‐oil compositions of buds harvested from the upper and lower parts of the shrubs was investigated by hierarchical clustering. All essential oils originating from the same genotype were grouped in the same cluster, indicating the reliability of essential oils as chemotaxonomic markers. For more detailed chemotaxonomic investigations, the three compounds with the greatest variance were chosen, i.e., sabinene, δ‐car‐3‐ene, and β‐phellandrene, which proved to be efficient for the variety distinction. Factor analysis showed that the essential‐oil composition as chemotaxonomic marker in blackcurrants was more reliable for variety Ben Sarek than for variety Ben Nevis. Moreover, it was demonstrated that the essential oils had very strong inhibitory activity against all tested microorganisms. Fungi were more sensitive than bacteria; indeed their growth was completely inhibited at much lower concentrations. In comparison to commercial antibiotics, significantly lower concentrations of the oils were necessary for the complete inhibition of fungal growth.     

Variation amongEucalyptus species in resistance to eucalyptus longhorned borer in Southern California

Eucalyptus L'Héritier (Myrtaceae: Leptospermoideae) species are native to the Austro-Malaysian region, but have been widely planted in temperate and subtropical regions around the world. In most regions whereEucalyptus have been imported, the Eucalyptus Longhorned Borer (Phoracantha semipunctata F.) (Coleoptera: Cerambycidae) has been accidently introduced. Larvae of the beetle bore through the bark and mine along the cambium of stressed trees, usually killing their host. We report here the relative susceptibilities of 12Eucalyptus species in two mixed-species plantations in California, USA. These trees were stressed by water deficit resulting from a prolonged drought.Eucalyptus species that appeared resistant to the borer includedE. camaldulensis Dehnhardt,E. cladocalyx F. Muller,e. sideroxylon A. Cunn. ex Woolls, andE. trabutii (anE. camaldulensis hybrid). Species that were more susceptible to attack wereE. diversicolor F. Mueller,E. globulus LaBillardière,E. grandis Hill ex Maiden,E. nitens (Deane & Maiden),E. saligna Sm., andE. viminalis LaBillardière. Survival of trees was influenced by fine-scale moisture variation resulting from slope and irrigation effects. Resistance characteristics of theseEucalyptus species did not correlate with taxonomic relatedness or bark characteristics, but did correspond to drought tolerance traits in their native habitat.Eucalyptus species that were resistant to attack byP. semipunctata were those that are most tolerant of drought in Australia.     

Non-volatile components of the essential oil secretory cavities of Eucalyptus leaves: Discovery of two glucose monoterpene esters, cuniloside B and froggattiside A

The essential oils extracted from the embedded foliar secretory cavities of many Eucalyptus species are of economic value as pharmaceuticals and fragrance additives. Recent studies have indicated that Eucalyptus secretory cavities may not be exclusively involved in the biosynthesis and storage of essential oils. Therefore, we selected three species upon which to perform an examination of the contents of foliar secretory cavities: Eucalyptus froggattii, E. polybractea and E. globulus. This paper describes the isolation and structural characterization of two non-volatile glucose monoterpene esters, which we have named cuniloside B and froggattiside A, from within the secretory cavities of these species, and shows the presence of these compounds in solvent extracts of the leaves from two other species of Eucalyptus. Both compounds were found in high proportions relative to the essential oils extracted from the leaves. We propose that many other carbohydrate monoterpene esters previously isolated from bulk leaf extracts of various Eucalyptus species may also be localized within the non-volatile fraction of foliar secretory cavities.     

Chemical composition and antibacterial activities of seven Eucalyptus species essential oils leaves

Background

In this paper, we have studied the essential oils chemical composition of the leaves of seven Eucalyptus species developed in Tunisia. Eucalyptus leaves were picked from trees growing in different arboretums in Tunisia. Choucha and Mrifeg arboretums located in Sedjnene, region of Bizerte (Choucha: E. maideni, E. astrengens et E. cinerea; Mrifeg : E. leucoxylon), Korbous arboretums located in the region of Nabeul, North East Tunisia with sub-humid bioclimate, (E. lehmani), Souiniet-Ain Drahem arboretum located in region of Jendouba (E. sideroxylon, E. bicostata). Essential oils were individually tested against a large panel of microorganisms including Staphylococcus aureus (ATCC 6539), Escherichia coli (ATCC 25922), Enterococcus faecalis (ATCC29212), Listeria ivanovii (RBL 30), Bacillus cereus (ATCC11778).

Results

The yield of essential oils ranged from 1.2% to 3% (w/w) for the different Eucalyptus species. All essential oils contain α-pinene, 1,8-cineol and pinocarveol-trans for all Eucalyptus species studied. The 1,8-cineol was the major compound in all species (49.07 to 83.59%). Diameter of inhibition zone of essential oils of Eucalyptus species varied from 10 to 29 mm. The largest zone of inhibition was obtained for Bacillus cereus (E. astrengens) and the lowest for Staphylococcus aureus (E. cinerea). The essential oils from E. maideni, E. astrengens, E. cinerea (arboretum of Bizerte), E. bicostata (arboretum of Aindraham) showed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus.

Conclusion

The major constituents of Eucalyptus leaves essential oils are 1,8-cineol (49.07 to 83.59%) and α-pinene (1.27 to 26.35%). The essential oils from E. maideni, E. astrengens, E. cinerea, E. bicostata showed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus, they may have potential applications in food and pharmaceutical products.     

Repellent,Insecticidal and Antimicrobial Activities of Leaf Essential Oils from Three Eucalyptus Species

Developing effective and eco‐friendly antimicrobials and pesticides has become a highly important issue. The repellent, insecticidal and antimicrobial activity of essential oils (EOs) isolated by hydrodistillation from dried leaves of the three Eucalyptus species (E. cloeziana, E. umbellata and E. benthamii) were investigated. During GC/MS analysis, α‐pinene (47.36 %), 1,8‐cineol (38.53 %) and α‐pinene (35.31 %) were identified as major components of E. cloeziana, E. umbellata and E. benthamii, respectively. The EOs from E. cloeziana exhibited the longest effective protection time (465 min, at 50.0 % w/w) for humans among the EOs studied. The effective protection time was 30 min and 300 min at concentrations of 12.5 % (w/w) and 25.0 % (w/w), respectively. Fumigating insecticidal activity of EOs from three Eucalyptus species was tested by airtight fumigation in conical flask, which indicated that essential oils had a highly and rapidly insecticidal activity on Culex pipiens quinquefasciatus. The antimicrobial activity of EOs was evaluated by using disc diffusion and agar dilution methods. There was no significant difference in the antibacterial activity of EOs from E. cloeziana and E. umbellate and they had the same MICs (20 mL/L) on Staphylococcus aureus, Salmonella typhi, Bacillus subtilis and Escherichia coli. E. benthamii had the worst microbial inhibitory effect among the three Eucalyptus essential oils and the MIC value for the test species is 40 mL/L except for Rhodotorula Harrison (10 mL/L).     

Chemical Diversity in Himalayan Elsholtzia Species

The terpenoid composition of essential oils from the leaves of five Elsholtzia species, viz., E. eriostachya Benth ., E. cristata Willd ., E. polystachya Benth ., E. flava Benth ., and E. pilosa Benth ., collected from the Himalayan region (India), was examined by GC, GC/MS, and NMR analyses. Comparison of the results with previous reports revealed new chemotypes. Cluster analysis was carried out in order to discern the similarities and differences within the essential‐oil compositions at their subspecies/chemotype level. Based on the major constituents of the essential oils, six chemical groups were obtained.     

Essential Oil Composition of Three Globularia Species

The chemical composition of the essential oils obtained by hydrodistillation from the aerial parts of Globularia cordifolia L., G. meridionalis (Podp.) O.Schwarz , and G. punctata Lapeyr . was characterized by GC‐FID and GC/MS analyses. Among the 33 identified compounds, the most abundant present in all investigated samples were oct‐1‐en‐3‐ol (2.9–47.0%), 6‐(1,5‐dimethylhex‐4‐enyl)‐3‐methylcyclohex‐2‐enone (8.2–40.9%), and fukinanolid (7.4–31.6%). Multivariate statistical analyses (PCA and HCA) of the hitherto studied Globularia volatile compounds confirmed to some extent the assumed phylogenetic relationships of the Globularia species studied, including the close relationship between the morphologically similar species G. cordifolia and G. meridionalis, but also evidenced several discrepancies in the current classification of Globularia species.     

The Chemical Diversity of Eucalyptus spp. Essential Oils from Plants Grown in Brazil

A chemical analysis of essential oils from leaves of eleven Eucalyptus L’Herit taxa, grown in Viçosa, Brazil were carried out. The identification and quantification of essential oils constituents were carried out by GC‐FID and GC/MS. The leaves of E. camaldulensis and E. tereticornis presented the highest oil content (3.00% and 2.30% respectively). In total, 48 compounds were identified in the oils. Higher levels of 1,8‐cineole were found for oils produced by E. microcorys (66.2%), E. urophylla (65.4%) and E. camaldulensis (44.8%) and the hybrid E. urophylla × E. grandis (33.0%). The oil from E. saligna was composed mainly by α‐pinene (92.3%). High concentrations of α‐phellandrene were found in the oils produced by E. camaldulensis (22.9%) and E. robusta (36.6%). The oils from E. grandis and E. pilularis were rich in p‐cymene (59.5% and 46.0%, respectively). Samples with high levels of 1,8‐cineole were classified by principal component analysis (PCA) using the accumulated variance of the PC1 and PC2 into major groups. Other samples were grouped based on their content of p‐cymene; α‐phellandrene, α‐ and β‐eudesmol; α‐pinene. The PCA allowed the separation and classification of samples with the highest levels of different compounds, a procedure that can help in the decision of grouping oils from different sources for industrial use.     

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.     

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.     

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.     

Volatiles of Geranium purpureum Vill. and Geranium phaeum L.: Chemotaxonomy of Balkan Geranium and Erodium Species (Geraniaceae)

The essential oils obtained by hydrodistillation of Geranium purpureum and G. phaeum were characterized by GC‐FID and GC/MS analyses (the former for the first time in general). In total, 154 constituents were identified, accounting for 89.0–95.8% of the detected GC peak areas. The investigated essential oils consisted mainly of fatty acids and fatty‐acid‐derived compounds (45.4–81.3%), with hexadecanoic acid and (E)‐phytol as the major components. The chemotaxonomic significance of the variations in the essential‐oil composition/production of the presently and previously investigated Geranium and highly related Erodium taxa from Serbia and Macedonia was assessed by multivariate statistical analyses. The main conclusions drawn from the high chemical similarity of the two genera, visible from the obtained dendrograms and biplots, confirm the close phylogenetic relationship between the investigated Geranium and Erodium taxa, i.e., that there is no great intergeneric oil‐composition variability. Changes in the composition and production of essential oils of the herein investigated taxa and 60 other randomly chosen species belonging to different plant genera were also statistically analyzed. The results put forward pro arguments for the oil‐yield–oil‐composition correlation hypothesis.     

Sensitivity of Aedes aegypti adults (Diptera: Culicidae) to the vapors of Eucalyptus essential oils

Vapors of essential oils extracted from various species of Eucalyptus (E. gunnii, E. tereticornis, E. grandis, E. camaldulensis, E. dunnii, E. cinerea, E. saligna, E. sideroxylon, E. globulus ssp. globulus, E. globulus ssp. maidenii, E. viminalis and the hybrids E. grandis × E. tereticornis and E. grandis × E. camaldulensis) and their major components were found to be toxic to Aedes aegypti adults, the yellow fever mosquito.An aliquot of each oil was placed in a cylindrical test chamber and the number of knocked-down mosquitoes was recorded as function of time. Knockdown time 50% was then calculated. Results showed that E. viminalis had the fastest knockdown time at of 4.2 min, on the same order as dichlorvos, a standard knockdown agent. A correlation was observed between the content of 1,8-cineole in the Eucalyptus essential oils and the corresponding toxic effect.The correlation between KT₅₀ values and calculated vapor pressures of the essential oil components showed that the fumigant activity of simple organic compounds in insects is correlated with their volatility.     

Essential‐Oil Variability of Juniperus deltoides R.P.Adams along the East Adriatic Coast – How Many Chemotypes Are There?

The composition of the essential oils isolated from twigs of ten Juniperus deltoides R.P . Adams populations from the east Adriatic coast was determined by GC‐FID and GC/MS analyses. Altogether, 169 compounds were identified, representing 95.6–98.4% of the total oil composition. The oils were dominated by monoterpenes (average content of 61.6%), which are characteristic oil components of species of the Juniperus section. Two monoterpenes, α‐pinene and limonene, were the dominant constituents, comprising on average 46.78% of the essential oils. Statistical methods were deployed to determine the diversity of the terpene classes and the common terpenes between the investigated populations. These statistical analyses revealed the existence of three chemotypes within all populations, i.e., a α‐pinene, limonene, and limonene/α‐pinene type.     

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.