Characterization by GC-MS of Vietnamese citrus species and hybrids based on the isotope ratio of monoterpene hydrocarbons

The isotope ratio of monoterpene hydrocarbons was used to characterize the citrus essential oils from different species and hybrids. Citrus cold-pressed peel oils from Vietnam were analyzed for the composition and isotope ratio of monoterpene hydrocarbons by using gas chromatography-mass spectrometry. A profile of citrus essential oils on the basis of their isotope ratio values and levels of monoterpene hydrocarbons was developed for Vietnamese citrus. The molecular isotope ratios were lower than those calculated from natural abundance of 13C and 2H. In addition, the isotope ratio of the base peaks (m/z 94/93) was significantly different among the citrus essential oils from different species and hybrids. The results would be applicable for the characterization of citrus essential oils from different origins.     

Isotope ratio analysis by HRGC-MS of monoterpene hydrocarbons from citrus essential oils

The isotope ratio of monoterpene hydrocarbons in citrus essential oils of different origins was measured by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). The isotope ratio (Ir) was determined by the ratio of the isotope peak intensity (m/z 137) to the molecular mass peak intensity (m/z 136) of the monoterpene hydrocarbons. The accuracy of Ir was examined by measuring monoterpene hydrocarbon standards and 13C-labeled compounds. The isotope fingerprints based on the values of monoterpene hydrocarbons from lemon, lime and yuzu essential oils were determined. These citrus essential oils were also discriminated by a principal component analysis of their Ir data. The characteristic vectors showed that alpha-terpinene, beta-pinene and beta-phellandrene were important components for distinguishing between the citrus species. It is suggested that this technique will be applicable to evaluate the quality, genuineness and origin of citrus fruits and their products.     

Salvia verbenaca L. essential oil: Variation of yield and composition according to collection site and phenophase

The effect of the collection sites and phenophase on yield and chemical composition of Salvia verbenaca essential oils was evaluated. The essential oil constituents were assessed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). The highest essential oil yields were observed for samples of the higher semi-arid bioclimate and at the flowering period. Eighty-five volatile constituents were identified and their percentages varied significantly (p < 0.05) depending on the collection site and the phenological stage. According to the plants origin, essential oils were dominated by monoterpene hydrocarbons, oxygenated monoterpenes and sesquiterpene hydrocarbons. The monoterpene hydrocarbons (31.9%) predominate at the flowering stage whereas oxygenated sesquiterpenes (27.5%) at the early fruiting stage. The sesquiterpene hydrocarbons (28.2%) was the most represented chemical class at late fruiting. On the basis of GC-MS data, the major identified volatile constituents were viridiflorol (3.4–17.7%), α-pinene (0.7–15.9%), β-caryophyllene (1.0–15.3%) and p-cymene (1.3–14.2%). S. verbenaca contains a diversity of bioactive constituents which shows large variations as affected by the collection sites and phenophase.     

Autooxidation of a mixture of lemon essential oils,methyl linolenoate,and methyl oleinate

Stability of components of a mixture of methyl linolenoate and methyl oleinate with two lemon (Citrus limon L.) essential oils in hexane during their autooxidation in light was studied by gas chromatography. The essential oils differed by their quantitative ratio of components: the single-fold (1x) oil contained approximately 90% monoterpene hydrocarbons and 1.47% citral, whereas the proportions of hydrocarbons and citral in the tenfold (10x) oil were approximately 60 and 18.32%, respectively. The concentration and composition of essential oils influence the rates of fatty-acid oxidation and fatty-acid peroxide cleavage. The 1x lemon oil inhibited the oxidation of methyl linolenoate and methyl oleinate, whereas the 10x oil accelerated these processes. The distinctions in the resistance of the major components of lemon essential oil to oxidation, which are determined by their composition and antioxidant properties of unsaturated fatty acids, were revealed.     

Isotope ratio by HRGC-MS of citrus Junos tanaka (yuzu) essential oils: m/z 137/136 of terpene hydrocarbons

The isotope ratios of monoterpene hydrocarbons in Citrus junos Tanaka (yuzu) essential oils from different origins were determined by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). Both intensities of the molecular mass peaks (m/z 136) and of the isotope peaks (m/z 137) of monoterpene hydrocarbons were measured by single-ion monitoring with an MS analysis. The isotope ratios (m/z 137/136) of the ten monoterpene hydrocarbons commonly contained in citrus essential oils, alpha-pinene, beta-pinene, sabinene, myrcene, alpha-phellandrene, alpha-terpinene, limonene, gamma-terpinene, beta-phellandrene and terpinolene, were determined in yuzu samples of the highest commercial quality from 42 different production districts. Statistical treatment of these data by the t-test and sign test revealed significant differences of the isotope effects in each yuzu sample. It is suggested that this technique will be applicable for evaluating the quality, genuineness and origin of citrus fruits and their products. The isotope fingerprints were also demonstrated in several citrus fruits other than the yuzu samples.     

Isotope Ratio by HRGC-MS of Citrus junos Tanaka (Yuzu) Essential Oils: m/z 137/136 of Terpene Hydrocarbons

The isotope ratios of monoterpene hydrocarbons in Citrus junos Tanaka (yuzu) essential oils from different origins were determined by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). Both intensities of the molecular mass peaks (m/z 136) and of the isotope peaks (m/z 137) of monoterpene hydrocarbons were measured by single-ion monitoring with an MS analysis. The isotope ratios (m/z 137/136) of the ten monoterpene hydrocarbons commonly contained in citrus essential oils, α-pinene, β-pinene, sabinene, myrcene, α-phellandrene, α-terpinene, limonene, γ-terpinene, β-phellandrene and terpinolene, were determined in yuzu samples of the highest commercial quality from 42 different production districts. Statistical treatment of these data by the t-test and sign test revealed significant differences of the isotope effects in each yuzu sample. It is suggested that this technique will be applicable for evaluating the quality, genuineness and origin of citrus fruits and their products. The isotope fingerprints were also demonstrated in several citrus fruits other than the yuzu samples.     

Analysis of the volatile essential oils of Murraya koenigii and Pandanus latifolius

Using well-established techniques, samples were obtained of the volatile essential oils of the two types of curry leaf, Murraya koenigii and Pandanus latifolius. Both contained mainly terpenes, and M. koenigii produced less than 4% of other components with eight monoterpene hydrocarbons (ca 16%) and 17 sesquiterpene hydrocarbons (ca 80%) being obtained. The most important constituents of M. koenigii are β-caryophyllene, β-gurjunene, β-elemene, β-phellandrene and β-thujene. The volatile essential oil of P. latifolius also contained mainly sesquiterpene hydrocarbons (6–42%) but the only monoterpene was linalool (ca 6%). Nearly 2000 times the total quantity of aroma volatiles was produced by M. koenigii compared with P. latifolius, and this partly explains the observed stronger flavour potency of the former.     

Essential oils from micropropagated plants of Lavandula viridis

The essential oils of Lavandula viridis were analysed by GC and GC-MS. Comparisons were made between three types of plant material from the same clone: field-grown plant, in vitro shoot cultures and micropropagated plants of the same clone. The most common components usually found in lavender oils were present in the oil samples analysed and more than 45 constituents were identified, representing more than 80% of the essential oil. The essential oils analysed consisted mainly of monoterpenes (75.4-76.3%), where oxygenated and hydrocarbons identified ranged from 41.8 to 57.3% and 18.1 to 34.2%, respectively. The major components found were 1.8-cineole (18.2-25.1%), camphor (9.1-15.7%), alpha-pinene (8.8-14.1%), borneol (4.1-4.8%), beta-pinene (1.2-5.6%), delta 3-carene (1.0-6.5%) and alpha-terpineol (0.8-4.2%). The monoterpene fraction of the in vitro shoot cultures showed different relative amounts of hydrocarbons and oxygenated components in relation to the parent plant and to micropropagated plants. In the sesquiterpene hydrocarbon fraction of the oil samples analysed (6.1-8.2%), 7-epi-alpha-selinene (1.6-4.8%) was the most important component and the oxygenated sesquiterpenes were found in small amounts (1.1-1.7%). The essential oils from field-grown plants of L. viridis, when compared with those obtained from in vitro shoot cultures or micropropagated plants of the same clone, demonstrated that the same major components were found without significant compositional variations.     

Enantioselective GC–MS analysis of volatile components from rosemary (Rosmarinus officinalis L.) essential oils and hydrosols

Essential oils and hydrosols were extracted from rosemary harvested in different seasons, and the chemical compositions of volatile components in the two fractions were analyzed by gas chromatography–mass spectrometry (GC–MS). Enantiomers of some volatile components were also analyzed by enantioselective GC–MS. Classification of aroma components based on chemical groups revealed that essential oils contained high levels of monoterpene hydrocarbons but hydrosols did not. Furthermore, the enantiomeric ratios within some volatile components were different from each other; for example, only the (S)-form was observed for limonene and the (R)-form was dominant for verbenone. These indicate the importance of determining the enantiomer composition of volatile components for investigating the physiological and psychological effects on humans. Overall, enantiomeric ratios were determined by volatile components, with no difference between essential oils and hydrosols or between seasons.     

Partial self‐incompatibility in the polyploid endemic species Scalesia affinis (Asteraceae) from the Galápagos: remnants of a self‐incompatibility system?

Different pollination treatments of capitula were used to examine the breeding system of individuals of the tetraploid endemic species Scalesia affinis from the Galápagos Islands. All types of crossings resulted in approximately 35 achenes per capitulum, but in actively and passively self-pollinated capitula these were mostly without embryos. Among self-pollinated individuals a large variation was found in the production of embryos. Some individuals failed completely to set filled achenes while others produced few or many. Additionally, we found a clear difference in female phenology of florets in self-pollinated capitula compared with florets in cross-pollinated capitula. Female florets in self-pollinated capitula remained receptive for longer time. These results suggest that Scalesia affinis is partly self-incompatible. Outcrossing is assured by the endemic carpenter bee, Xylocopa darwini , which proved to be an important pollinator of Scalesia affinis . Nevertheless, geitonogamy seemed to be considerable in the focal population, for which reason open pollinated capitula produced fewer achenes than controlled outcrossed capitula.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 93–101.     

Chemical Composition and Biological Activities of Tunisian Cupressus arizonica Greene Essential Oils

The chemical composition of the essential oils obtained by hydrodistillation of leaves, stems, and female cones of Cupressus arizonica Greene , grown in Tunisia, was studied by GC‐FID and GC/MS analyses. Altogether, 62 compounds were identified, 62 in the leaf oil, 19 in the cone oil, and 24 in the stem oil. The cone and stem oils were mainly composed by monoterpene hydrocarbons (96.6 and 85.2%, resp.). In the leaf oil, the total sesquiterpene fraction constituted 36.1% and that of the monoterpene hydrocarbons 33.8% of the total oil composition. The three oils were evaluated for their in vitro herbicidal activity by determining their influence on the germination and the shoot and root growth of the four weed species Sinapis arvensis L., Lolium rigidum Gaudin , Trifolium campestre Schreb ., and Phalaris canariensis L. At the highest doses tested (0.8 and 1.0 mg/ml), the leaf essential oil inhibited either totally or almost completely the seed germination and the shoot and root growth of S. arvensis and T. campestre. The oils were also tested for their antifungal activity; however, their effects on the fungal growth were statistically not significant.     

A comparative study of ×Cupressocyparis leylandii clones (Cupressaceae) by gas chromatographic analysis of their leaf oils*

The essential oils isolated from foliage of various clones of x Cupressocyparis leylandzi were analyzed by gas chromatography to determine whether the oils could be used as aids in clonal identification. Several botanical gardens supplied foliage which was submitted to hydrodistillation. The oils were isolated under standardized conditions and then analyzed. Comparison of the oil components (mostly monoterpene hydrocarbons) revealed that it is possible to identify, on the basis of the composition of the monoterpene hydrocarbon mixture, clones 1–6 as a group and clones 10 and 11 individually. The composition of the oils from foliage of the widely propagated clones 1,2, 10 and 11 is given in more detail.     

Essential oil of Daucus glaber Forssk

The composition of the essential oil of the fruits, leaves and stems of Daucus glaber Forssk has been studied by GC/MS. It was found that, the essential oil of the fruits consists of monoterpene hydrocarbons (limonene and sylvestrene are the majors) and phenylpropanoids (elemicin is the major). Sylvestrene has never been reported before in the essential oil of any Daucus species. The study of the essential oil of the leaves revealed the presence of monoterpene hydrocarbons; limonene and gamma-terpinene are the majors and a small amount of sylvestrene. The essential oil of stems consists of monoterpene hydrocarbons (gamma-terpinene is the major), terpene alcohols (mainly 4-terpineol) and phenylpropanoids (myristicin and elemicin are the majors). It is interesting that, the essential oil of the fruits is free from any oxygenated terpenes while that of the stems is free from limonene and sylvestrene which are present in the essential oil of the fruits and leaves in fairly large amounts The essential oil of the fruits, leaves and stems shows broad antimicrobial activities against both gram positive and gram negative bacteria. In addition, the volatile oil of the stem, particularly, show activities against Candida albicans (yeast). Also, the prepared oils have variable cytotoxic activities with LC50 21.52, 36.01 and 42.34 microg/ml, respectively.     

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)‐β‐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 composition of Thuja orientalis L. essential oils and study of their allelopathic potential on germination and seedling growth of weeds

The chemical composition of essential oils isolated by hydrodistillation from needles and cones of Thuja orientalis L. was analysed by gas chromatography-flame ionisation detection and gas chromatography–mass spectrometry. Twenty-one compounds were identified; quantitative differences, mainly, between cone and needle oils were observed. Both oils were rich in monoterpene hydrocarbons and the major constituents were α-pinene (64.2 and 49.3%, respectively, in cones and needles), β-phellandrene (6.7–9.6%) and α-cedrol (3.9 and 8.2%). Herbicidal properties of Thuja essential oils were assessed against three invasive weed species in crops: Sinapis arvensis L., Phalaris paradoxa L. and Lolium rigidum Gaud. The study of herbicidal activity was carried out on the weed germination, seed vigour and seedling growth. Our results showed a strong inhibitory effect on all tested weeds following a dose-dependent manner, property that could be valourised in managing biocontrol of weeds.     

Chemotaxonomic significance of the essential oils of 18 Ferula species (Apiaceae) from Iran

To evaluate the chemotaxonomic significance of the essential oils of 23 populations of 18 Iranian Ferula species, the chemical composition of the oils was investigated by GC/FID and GC/MS. Altogether, 84 constituents, representing 81.3-99.7% of the total composition of the oils, have been identified. The composition of six species of the genus, i.e., F. oopoda, F. foetida, F. behboudiana, F. diversivittata, F. galbaniflua, and F. hezarlalehzarica, has been reported for the first time. The main constituents identified were α-terpinyl acetate (73.3%), 2,3,4-trimethylthiophene (2; 49.0%), sabinene (75.3%), verbenone (5; 69.4%), β-pinene (59.0-66.3%), and (Z)-β-ocimene (41.7%). Cluster analysis (CA) of the percentage content of the essential oil components of the Ferula species resulted in the characterization of four groups, i.e., taxa containing either i) monoterpene hydrocarbons, ii) oxygenated monoterpenes, iii) organosulfur compounds, or iv) monoterpene, sesquiterpene, and aliphatic hydrocarbons as the principal classes of compounds. Based on the results obtained, the chemical independence of F. hirtella from F. szowitsiana and of F. galbaniflua from F. gummosa at the specific level was concluded and their positions as distinct species were confirmed. The chemotaxonomic relationships among the representatives of the genus Ferula have been discussed in detail.     

Chemical composition and bioactivity of Boswellia serrata Roxb. essential oil in relation to geographical variation

Oleo–gum–resin of Boswellia serrata Roxb. (Burseraceae) was collected from Shivpuri forest situated in northwestern district of Madhya Pradesh, India. The commercial samples were purchased from Mandsaur and Neemuch districts (the major herbal markets of Madhya Pradesh) for comparative study of their essential oils. The average essential oil contents in the commercial Neemuch samples (11.1%) were much better as compared to the wild collection from Shivpuri (6.1%) as well as commercial collection from Mandsaur (6.9%). The commercial samples contained higher percentage of monoterpene hydrocarbons (81.9–88.1%) including α-thujene (61.4–69.8%) as the major compound. The wild habitat contained higher percentage of oxygenated monoterpenoids/benzenoids (15.7%) and sesquiterpenes (19.2%) including α-terpineol (7.8%), terpinyl isobutyrate (5.1%), and eudesmol (11.5%). Further, the antimicrobial activities of these collections showed remarkable variation among the essential oils. On the other hand, wild habitat contained improved percentage of semi-polar compounds (34.9%) which might be responsible for enhanced antibacterial activity. Similarly, the winter collection from Neemuch (BS-N2) showed significant antioxidant activity, whereas the wild habitat did not show any antioxidant activity. The higher percentage of monoterpene hydrocarbons in commercial samples, especially δ-3-carene, α-pinene, and α-thujene, might be responsible for enhanced antifungal and antioxidant activities. The Pearson correlation values justify the bioactivity relationship of the major compounds with different microbial strains. It also justified the interaction among the major individual compounds.     

Chemical composition,aphicidal and antiacetylcholinesterase activities of essential oils against Aphis nerii Boyer de Fonscolombe (Hemiptera: Aphididae)

Aphids are important sucking insects that attack many crops and cause huge economic loss. Essential oils have been proposed to be appropriate alternative to synthetic insecticides due to their low impact on environment and human health. In this work, the chemical compositions of eight essential oils extracted from plants growing in Egypt were determined by gas chromatography/mass spectrometry (GC–MS). The aphicidal activities of the isolated oils were examined against the adults of oleander aphid, Aphis nerii by a leaf-dipping assay. The inhibitory effect of essential oils on acetylcholinesterase (AChE) activity was also tested in vitro. Chemical analyses showed the essential oils consisted mainly of monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons and oxygenated sesquiterpenes except the oil of Artemisia monosperma which contained high content of benzenes. The results of toxicity assay showed that the oils of A. monosperma and Citrus sinensis were the most potent toxicants displaying LC₅₀ value of 0.06 mg/L. The oils of Callistemon viminals, Schinus terebinthifolius and Schinus molle were also highly effective against aphid as their LC₅₀ values were lower than 1 mg/L. In addition, the highest inhibitory effect on AChE was recorded by 0.5 mg/L C. sinensis with inhibition of 49.33%, while 0.1 mg/L Citrus lemon oil recorded the lowest inhibitory effect with inhibition of 0.4%. In general, six of tested essential oils showed high toxicity against A. nerii and they might be applied in the IPM programs for this insect.     

MS fragment isotope ratio analysis for evaluation of citrus essential oils by HRGC-MS

To evaluate the origin of citrus essential oils, the isotope ratio of fragment peaks on HRGC-MS of the volatile compounds from various citrus oils was measured. The MS fragment ratio was found by the ratio of fragment peak intensity, m+1/m (m/z). This ratio reflects the isotope effect of volatile compounds, that is, it provides information about locality, quality, and species for essential oils. Multivariate analysis based on the MS fragment ratio of monoterpene hydrocarbons clearly distinguished three citrus species, yuzu, lemon, and lime. The carbonyl fractions were also extracted from citrus essential oils by the sodium hydrogensulfite method. The isotope ratio of MS fragments of octanal, nonanal, and decanal was also examined. The results suggest that there was no significant difference in the individual fragment isotope ratios of the three aldehydes.     

Genetic structure and essential oil composition in wild populations of Salvia multicaulis Vahl.

The phytochemical study on ten populations of Salvia multicaulis Vahl. revealed that their essential oil qualitative profiles contained a significant amount of monoterpene hydrocarbons, which were the most abundant compounds. Besides, α-Pinene was the major constituent in all studied populations' essential oils. Significant correlations were observed between edaphic parameters and some major essential oil compounds. According to clustering analyses of the chemical data, the S. multicaulis populations were divided into three chemotypes: β-caryophyllene, camphene and camphor, and limonene. The population genetics study showed significant molecular differences among the populations. The Mantel test indicated a significant positive correlation between the geographical distances and genetic diversity, exhibiting a low amount of gene flow and a considerable genetic differentiation value. We also detected four genotypes based on the Nei's genetic distance and structure analysis. The identified chemical and genetic similarities/differences among these populations were correlated with edaphic parameters and geographic distances, suggesting that environmental factors are the primary drivers of the chemical polymorphism of essential oils in S. multicaulis populations.