Enantiomers Of Α-pinene Research Articles

Enantiomeric composition of α-pinene affects catches of bark and wood boring beetles, and associated species, in ethanol-baited multiple-funnel traps.

In 2009, we determined the effects of the enantiomeric composition of the kairomone, α-pinene, on trap catches of arboreal beetles (Coleoptera) in stands of eastern pine trees with resin dominated by (+)-α-pinene. We hypothesized that the responses of beetles would correlate with the predominant enantiomer of α-pinene found in host pines. Lures of (+)-, racemic (±), and (-)-α-pinene were added separately to ethanol-baited multiple-funnel traps. Species such as Monarthrum mali (Fitch), Dendroctonus terebrans (Olivier), Ips grandicollis (Eichhoff), and Pachylobius picivorus (Germar) (Coleoptera: Curculionidae) showed a preference for traps co-baited with (-)-α-pinene. α-Pinene enhanced attraction of Hylastes salebrosus Eichhoff, Hylastes porculus Erickson and Hylastes tenuis Eichhoff (Coleoptera: Curculionidae) to ethanol-baited traps with no effects from enantiomeric composition of α-pinene. The attraction of the ambrosia beetles, Xyleborinus saxesenii (Ratzeburg) and Dryoxylon onoharaense (Murayama) (Coleoptera: Curculionidae) to ethanol-baited traps was interrupted by the addition of α-pinene, regardless of enantiomeric composition. Species such as Xylosandrus germanus (Blandford), Cnestus mutilatus (Blandford) and Stenoscelis brevis (Boheman) (Coleoptera: Curculionidae) were unaffected by the presence of α-pinene. Trap catches of some species of longhorn beetles and bark beetle predators (Coleoptera: Cerambycidae, Cleridae, Elateridae, Histeridae, and Trogossitidae) were increased by the addition of α-pinene, although results varied by location. Platysoma spp. (Coleoptera: Histeridae) showed a marked preference for traps co-baited with (+)-α-pinene in Florida and Georgia. In summary, we found that the enantiomeric composition of α-pinene in hosts was not a good predictor of enantiomeric preferences by beetles.

Evolution and functional role prediction of the CYP6DE and CYP6DJ subfamilies in Dendroctonus (Curculionidae: Scolytinae) bark beetles.

Dendroctonus-bark beetles are natural components and key ecological agents of coniferous forests. They spend most of their lives under the bark, where they are exposed to highly toxic terpenes present in the oleoresin. Cytochrome P450 (CYP) is a multigene family involved in the detoxification of these compounds. It has been demonstrated that CYP6DE and CYP6DJ subfamilies hydroxylate monoterpenes, whose derivatives can act as pheromone synergist compounds or be pheromones themselves in these insects. Given the diversity and functional role of CYPs, we investigated whether these cytochromes have retained their function throughout the evolution of these insects. To test this hypothesis, we performed a Bayesian phylogenetic analysis to determine phylogenetic subgroups of cytochromes in these subfamilies. Subgroups were mapped and reconciled with the Dendroctonus phylogeny. Molecular docking analyses were performed with the cytochromes of each subgroup and enantiomers of α-pinene and β-pinene, (+)-3-carene, β-myrcene and R-(+)-limonene. In addition, functional divergence analysis was performed to identify critical amino acid sites that influence changes in catalytic site conformation and/or protein folding. Three and two phylogenetic subgroups were recovered for the CYP6DE and CYP6DJ subfamilies, respectively. Mapping and reconciliation analysis showed different gain and loss patterns for cytochromes of each subgroup. Functional predictions indicated that the cytochromes analyzed are able to hydroxylate all monoterpenes; however, they showed preferential affinities to different monoterpenes. Functional divergence analyses indicated that the CYP6DE subfamily has experimented type I and II divergence, whereas the CYP6DJ subfamily has evolved under strong functional constraints. Results suggest cytochromes of the CYP6DE subfamily evolve to reinforce their detoxifying capacity hydroxylating mainly α- and β-pinene to (+) and (-)-trans-verbenol, being the negative enantiomer used as a pheromone by several Dendroctonus species; whereas cytochromes of the CYP6DJ subfamily appear to retain their original function related to the detoxification of these compounds.

A New Essential Oil from the Leaves of Gynoxys rugulosa Muschl. (Asteraceae) Growing in Southern Ecuador: Chemical and Enantioselective Analyses.

An essential oil, distilled from the leaves of the Andean species Gynoxys rugulosa Muschl., is described in the present study for the first time. The chemical composition was qualitatively and quantitatively determined by GC-MS and GC-FID, respectively. On the one hand, the qualitative composition was obtained by comparing the mass spectrum and the linear retention index of each component with data from literature. On the other hand, the quantitative composition was determined by calculating the relative response factor of each constituent, according to its combustion enthalpy. Both analyses were carried out with two orthogonal columns of nonpolar and polar stationary phases. A total of 112 compounds were detected and quantified with at least one column, corresponding to 87.3-93.0% of the whole oil mass. Among the 112 detected components, 103 were identified. The main constituents were α-pinene (5.3-6.0%), (E)-β-caryophyllene (2.4-2.8%), α-humulene (3.0-3.2%), germacrene D (4.9-6.5%), δ-cadinene (2.2-2.3%), caryophyllene oxide (1.6-2.2%), α-cadinol (3.8-4.4%), 1-nonadecanol (1.7-1.9%), 1-eicosanol (0.9-1.2%), n-tricosane (3.3-3.4%), 1-heneicosanol (4.5-5.8%), n-pentacosane (5.8-7.1%), 1-tricosanol (4.0-4.5%), and n-heptacosane (3.0-3.5%). Furthermore, an enantioselective analysis was carried out on the essential oil, by means of two cyclodextrin-based capillary columns. The enantiomers of α-pinene, β-pinene, sabinene, α-phellandrene, β-phellandrene, linalool, α-copaene, terpinen-4-ol, α-terpineol, and germacrene D were detected, and the respective enantiomeric excess was calculated.

Chiral monoterpenes reveal forest emission mechanisms and drought responses

Monoterpenes (C10H16) are emitted in large quantities by vegetation to the atmosphere (>100 TgC year−1), where they readily react with hydroxyl radicals and ozone to form new particles and, hence, clouds, affecting the Earth’s radiative budget and, thereby, climate change1–3. Although most monoterpenes exist in two chiral mirror-image forms termed enantiomers, these (+) and (−) forms are rarely distinguished in measurement or modelling studies4–6. Therefore, the individual formation pathways of monoterpene enantiomers in plants and their ecological functions are poorly understood. Here we present enantiomerically separated atmospheric monoterpene and isoprene data from an enclosed tropical rainforest ecosystem in the absence of ultraviolet light and atmospheric oxidation chemistry, during a four-month controlled drought and rewetting experiment7. Surprisingly, the emitted enantiomers showed distinct diel emission peaks, which responded differently to progressive drying. Isotopic labelling established that vegetation emitted mainly de novo-synthesized (−)-α-pinene, whereas (+)-α-pinene was emitted from storage pools. As drought progressed, the source of (−)-α-pinene emissions shifted to storage pools, favouring cloud formation. Pre-drought mixing ratios of both α-pinene enantiomers correlated better with other monoterpenes than with each other, indicating different enzymatic controls. These results show that enantiomeric distribution is key to understanding the underlying processes driving monoterpene emissions from forest ecosystems and predicting atmospheric feedbacks in response to climate change.

Measurement of enantiomer percentages for five monoterpenes from six conifer species by cartridge-tube-based passive sampling adsorption–thermal desorption (ps-ATD)

Abstract. Many monoterpenes have at least two different stereochemical forms, and many biosynthetic pathways are known to favor one product over the other(s). A rapid method was developed and used in the determination of the (-/+)-enantiomeric distributions for α-pinene, β-pinene, camphene, limonene, and β-phellandrene as emitted by plant material from six conifer species. The six species included the two pine species Pseudotsuga menziesii and Pinus ponderosa, as well as the four cypress species Chamaecyparis lawsoniana, Thuja plilcata, Juniperus chinensis, and Thuja occidentalis. The method involved passive sampling adsorption–thermal desorption (ps-ATD). During sampling, the cartridge tube was placed in a 60 mL glass vial with plant material for 1 h. Sample analytes were thermally transferred to a chiral gas chromatography (GC) column. Detection was by mass spectrometry (MS). The six species exhibited different emission patterns for the five monoterpenes in the -/+ totals, although within a given species the distributions among the five monoterpenes were similar across multiple plants. β-pinene dominated in P. menziesii and P. ponderosa, and α-pinene dominated in T. plicata and T. occidentalis. The chiral separations revealed differences in the -/+ enantiomeric distributions among the species. The (−)-enantiomers of α-pinene and β-pinene dominated strongly in P. menziesii and P. ponderosa; the (−)-enantiomer of β-phellandrene dominated in C. lawsoniana. The dependence of the method precision on percent enantiomer abundance is discussed.

Possibility of chiral recognition by adsorption on enantiomorphous crystals: the impact of crystal surface polarity.

Chiral crystals remain one of the probable sources of first minute chiral symmetry breaking, a trigger that potentially causes an as-yet unknown type of asymmetric autocatalysis during the formation of chiral biopolymers under the conditions of the Archean Earth. Therefore, studying adsorption processes on the surface of such crystals may help improve the understanding of the nature of the initial chiral shift. The adsorptive activity of non-porous crystals with respect to the majority of organic molecules essentially depends on the ability of a crystal surface to engage in specific intermolecular interactions. In this work, the enantioselectivity provided by hippuric acid and phloroglucinol crystals, obtained under Viedma ripening conditions, was studied by the adsorption of menthol enantiomers from solutions and the adsorption of limonene and α-pinene enantiomers from vapors. To establish the reliability of chiral recognition, the experimental adsorption isotherms on chiral crystals were compared with the isotherms on achiral (racemic mixtures) crystals, obtained under similar conditions. The data obtained were confirmed using CD spectra, XRD patterns and SEM images. A t-test was used to assess the statistical significance of differences in adsorption. From the adsorption isotherms of vapors at different temperatures, the isosteric heats of adsorption and the differential entropies of adsorption were calculated. It was determined that the chiral recognition ability depends not only on the difference between enantiomers in the thermodynamic functions of adsorption, but also on the isosteric heats of adsorption at low coverages and the heat of liquefaction ratio. If intermolecular interactions between the enantiomer and the surface are too weak, then enantiomer layer formation becomes difficult. This reduces the enantioselectivity or even makes chiral recognition impossible. The physicochemical regularities revealed in this present work made it possible to formulate the requirements that enantiomorphous crystals must meet for satisfactory chiral recognition of molecules of different polarities.

High performance continuous-wave laser cavity enhanced polarimetry using RF-induced linewidth broadening.

We present precise optical rotation measurements of gaseous chiral samples using near-IR continuous-wave cavity-enhanced polarimetry. Optical rotation is determined by comparing cavity ring-down signals for two counter-propagating beams of orthogonal polarisation which are subject to polarisation rotation by the presence of both an optically active sample and a magneto-optic crystal. A broadband RF noise source applied to the laser drive current is used to tune the laser linewidth and optimise the polarimeter, and this noise-induced laser linewidth is quantified using self-heterodyne beat-note detection. We demonstrate the optical rotation measurement of gas phase samples of enantiomers of α-pinene and limonene with an optimum detection precision of 10 µdeg per cavity pass and an uncertainty in the specific rotation of ∼0.1 deg dm-1 (g/ml)-1 and determine the specific rotation parameters at 730 nm, for (+)- and (-)-α-pinene to be 32.10 ± 0.13 and -32.21 ± 0.11 deg dm-1 (g/ml)-1, respectively. Measurements of both a pure R-(+)-limonene sample and a non-racemic mixture of limonene of unknown enantiomeric excess are also presented, illustrating the utility of the technique.

Chiral Templating of Polycarbonate Membranes by Pinene Using the Modified Atomic Layer Deposition Approach.

In this article, chiral templating of a polycarbonate (PC) membrane by (-)-α-pinene using the atomic layer deposition (ALD) approach is investigated. The templating with the enantiomer of (-)-α-pinene, used as a case compound, was performed either on the original commercial PC membrane or on the PC membrane with a beforehand deposited Al2O3 layer. The efficiency of the templating was assessed by a difference in the membrane ability to adsorb/absorb (-)-α-pinene, (+)-α-pinene, and their racemic mixture, using a very sensitive gas sorption analyzer. The results clearly show that the solution-diffusion mechanism rather than the sieving mechanism applied for adsorption/absorption of (-/+)-α-pinene enantiomers, which have the same size of the molecule. The PC membrane with the predeposited Al2O3 before the (-)-α-pinene templating shows significantly higher sorption of (-)-α-pinene compared to (+)-α-pinene and racemate, which clearly demonstrates the presence of a chiral recognition effect.

The cytochrome P450 CYP6DE1 catalyzes the conversion of \u03b1-pinene into the mountain pine beetle aggregation pheromone trans-verbenol

The recent outbreak of the mountain pine beetle (Dendroctonus ponderosae; MPB) has affected over 20 M hectares of pine forests in western North America. During the colonization of host trees, female MPB release the aggregation pheromone (−)-trans-verbenol. (−)-trans-Verbenol is thought to be produced from the pine defense compound (−)-α-pinene by cytochrome P450 (P450) dependent hydroxylation. MPB may also use P450s for the detoxification of other monoterpenes of the pine defense system. Here we describe the functional characterization of MPB CYP6DE1. CYP6DE1, but not the closely related CYP6DE2, used the bicyclic monoterpenes (−)-α-pinene, (+)-α-pinene, (−)-β-pinene, (+)-β-pinene and (+)-3-carene as substrates. CYP6DE1 was not active with other monoterpenes or diterpene resin acids that were tested as substrates. trans-Verbenol is the major product of CYP6DE1 activity with (−)-α-pinene or (+)-α-pinene as substrates. When tested with blends of different ratios of (−)-α-pinene and (+)-α-pinene, CYP6DE1 produced trans-verbenol with an enantiomeric profile that was similar to that produced by female MPB exposed to the α-pinene enantiomers.

Antibacterial Activity and Time-kill Kinetics of Positive Enantiomer of α-pinene Against Strains of Staphylococcus aureus and Escherichia coli.

Research on new antimicrobial agents is needed, as more and more microorganisms that cause antibiotic-resistant diseases are emerging commercially. In this group, we can find strains of Staphylococcus aureus and Escherichia coli, which are highly opportunistic species. Faced with this perspective, research using essential oils present in plants is emerging as a therapeutic alternative for the treatment of antimicrobial infections. Many of these oils have, in their composition, monoterpene α-pinene, that shows to have antibacterial activity. The purpose of this research is to evaluate the antimicrobial activity of the positive enantiomer of α-pinene against strains of Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922. The methodologies used were: Disc-diffusion test, broth microdilution and bacterial death kinetics, all of which were standardized by CLSI. As a result, inhibition halos of 11 mm was obtained for the gram-positive strain and 12 mm for the gram-negative strain, both at the same concentration, 160 µl / ml. In addition, it was possible to observe with the death curve that the concentrations (1.25 µl/mL and 2.5 µl/mL of the (+)-α-pinene were able to eliminate the formation of bacterial colonies at one time of exposure of 2 hours for the E. coli strain. However, the death curve of the S. aureus strain was characterized by non-elimination of bacterial colonies at a 24 hours exposure time used for the experiment. Only amikacin evidenced its bacterial killing rate of all colonies within two hours of exposure. At the end, it was possible to verify the activity of the phytoconstituent against Escherichia coli strains ATCC 25922 and Staphylococcus aureus ATCC 25923, recommending the continuity of the studies with the use of different methodologies so that (+) - α-pinene in the future can be a compound used in antimicrobial therapy.

Toxicity of Pine Monoterpenes to Mountain Pine Beetle

The mountain pine beetle (Dendroctonus ponderosae; MPB) is an eruptive bark beetle species affecting pine forests of western North America. MPB are exposed to volatile monoterpenes, which are important host defense chemicals. We assessed the toxicity of the ten most abundant monoterpenes of lodgepole pine (Pinus contorta), a major host in the current MPB epidemic, against adult MPB from two locations in British Columbia, Canada. Monoterpenes were tested as individual volatiles and included (−)-β-phellandrene, (+)-3-carene, myrcene, terpinolene, and both enantiomers of α-pinene, β-pinene and limonene. Dose-mortality experiments identified (−)-limonene as the most toxic (LC50: 32 μL/L), and (−)-α-pinene (LC50: 290 μL/L) and terpinolene (LC50: >500 μL/L) as the least toxic. MPB body weight had a significant positive effect on the ability to survive most monoterpene volatiles, while sex did not have a significant effect with most monoterpenes. This study helps to quantitatively define the effects of individual monoterpenes towards MPB mortality, which is critical when assessing the variable monoterpene chemical defense profiles of its host species.

A helically folded poly(m,p-phenylene)

Two amphiphilic poly(m,p-phenylene)s were synthesized through Suzuki polycondensation from 1,3-phenylene dibromide bearing solubilizing tri- or tetra(ethylene glycol) chains and 1,4-phenylene diboronic acid diester. Unlike its tri(ethylene glycol)-functionalized congener the polymer with tetra(ethylene glycol) chains was shown to possess considerably high molecular weight (Mw=15,900 and Mn=7300) and good solubility in both polar and nonpolar organic solvents. Fluorescence spectra of the polymer recorded in CHCl3 and aqueous acetonitrile revealed that in the latter solution the fluorescence intensity is considerably lower and the band is redshifted by about 70 nm compared to the former one. This indicates a transition from a random coil conformation to an ordered compact one. A convincing indication of helical folding of the polymer came from an induced circular dichroism spectroscopic study of inclusion complexes of the tubular helical folds with α-pinene enantiomers influencing the sense of the helix.

Variation of essential oil yield and relative amounts of enantiomers of α-pinene in leaves and unripe cones of Juniperus communis L. growing wild in Lithuania

The variations in essential oil yields and enantiomeric composition of α-pinene in leaves and unripe cones of Juniperus communis between populations as well as at individual plant level were studied. Leaf and cone samples of total 110 J. communis individuals were collected from eleven habitats (in ten individuals from each habitat) representing a variety of edaphoclimatic conditions across Lithuania. Essential oils were analyzed by chiral-phase capillary gas chromatography (GC). The amount of essential oil yield varied from 0.3% to 4.2% in unripe cones and from 0.1% to 0.9% in leaves. (1R)-(+)-α-pinene prevailed over the (1S)-(−)-α-pinene amounting to 74±13% in leaves and 69±17% in unripe cones, and 26±13% in leaves and 31±17% in unripe cones, respectively. Only the total yield of essential oils in leaves varied significantly between populations (F=3.1, p<0.05). The highest averages of yields of essential oils were established in habitats with lower precipitation, higher temperatures and lower solar radiation.

Characterization of Volatile Components of Zingiber roseum Essential Oil Using Capillary GC on Modified Cyclodextrins

The essential oil from different parts of Zingiber roseum plants was extracted by hydrodistillation, and analyzed using enantio-GC, capillary-GC and GC-MS. Two chiral selectors, 6-tert-butyldimethylsilyl-2,3-diethyl-beta-cyclodextrin (TBDE-beta-CD), and 2,3,6-methyl-beta-cyclodextrin (PM-beta-CD) doped into 14% cyanopropylphenyl/86% dimethylpolysiloxane, and 35% diphenyl/65% dimethylpolysiloxane, respectively were compared in order to clarify the stereochemistry and enantioselectivity of terpenoids using chiral gas chromatography. The enantiomeric excess for (1R)-(+)-alpha-pinene, (1R)-(+)-beta-pinene, and (R)-(+)-limonene were characteristic for the rhizome. In TBDE-beta-cyclodextrin coated chiral columns, a significant increase in separation factor (alpha) for beta-pinene, limonene, linalool and alpha-terpineol enantiomers was observed when compared with methyl substituted beta-cyclodextrin. The increase in chain length of the alkyl substituents may be the possible cause for enantiomer separation in beta-cyclodextrin cavity. In addition, enantioreversal of alpha-pinene enantiomers in 6-tert-butyldimethylsilyl-2,3-diethyl-beta-cyclodextrin was noticed as a unique feature. The enantiomeric compositions of Z. roseum fruit and flower essential oils were similar, but, in contrast, the rhizome oil contained an entirely different composition. Therefore, these results aid in the authentication of the natural origin of Z. roseum essential oils.

Functional characterization of myrcene hydroxylases from two geographically distinct Ips pini populations

Ips pini bark beetles use myrcene hydroxylases to produce the aggregation pheromone component, ipsdienol, from myrcene. The enantiomeric ratio of pheromonal ipsdienol is an important prezygotic mating isolation mechanism of I. pini and differs among geographically distinct populations. We explored the substrate and product ranges of myrcene hydroxylases (CYP9T2 and CYP9T3) from reproductively-isolated western and eastern I. pini. The two cytochromes P450 share 94% amino acid identity. CYP9T2 mRNA levels were not induced in adults exposed to myrcene-saturated atmosphere. Functional assays of recombinant enzymes showed both hydroxylated myrcene, (+)- and (−)-α-pinene, 3-carene, and R-(+)-limonene, but not α-phellandrene, (−)-β-pinene, γ-terpinene, or terpinolene, with evidence that CYP9T2 strongly preferred myrcene over other substrates. They differed in the enantiomeric ratios of ipsdienol produced from myrcene, and in the products resulting from different α-pinene enantiomers. These data provide new information regarding bark beetle pheromone evolution and factors affecting cytochrome P450 structure–function relationships.

Odors of Norway spruce (Picea abies L.) seedlings: differences due to age and chemotype

Small conifer seedlings (mini-seedlings) are less damaged by the large pine weevil Hylobius abietis (L.) (Coleoptera: Curculionidae) compared to conventional seedlings. Chemical difference between the seedling types is one possible explanation for this phenomenon. In the present paper, the emissions of volatile organic compounds (VOC) of 7- to 43-week-old Norway spruce [Picea abies (L.) Karst.] seedlings were analyzed. Collection and identification of the volatiles was made by solid phase micro-extraction and gas chromatography mass spectrometry (SPME–GC–MS). The enantiomers of α-pinene and limonene were separated in a two-dimensional GC (2D-GC). Most of the seedlings represented either a limonene- or a bornyl acetate-chemotype. Only minor changes in the volatile composition of the two types of seedlings were found during the first year. Age-related changes, however, were found in the volatiles released by wounded phloem where green leaf volatiles (GLVs) and borneol were the dominated VOC for young seedling. The attractive compound for the pine weevil, α-pinene, was first detected in the phloem emissions of 18- to 22-week-old seedlings. Different storage conditions of the seedlings during the winter/early spring-phase influenced the volatile composition in the phloem. High amount of GLVs was characteristic for the 43-week-old seedlings stored in naturally changing outdoor temperature, but not present in the seedlings winter-stored at a constant temperature of −4 °C. The possible role of these observed differences in odor emissions between seedlings of different age and physiological status for the feeding preferences of the large pine weevil is discussed.

PRELIMINARY INVESTIGATION ON VOLATILE TERPENE PROFILES FROM IN VITRO SHOOT CULTURES OF THYMUS VULGARIS L. CLONES

Thymus spp. serve as a natural source of essential oils, fresh and dried herbs, extensively used all around the world both in medicine and in cosmetic and alimentary industries. Essential oils of T. vulgaris have been reported to be among the top 10 essential oils. Objective of this preliminary investigation was to characterize different clones of T. vulgaris in vitro shoot cultures based on their volatile terpene composition. For this purpose, in vitro shoot cultures were established by transferring the excised shoot tips of in vitro germinated seedlings on semi-solid MS medium, supplemented with 1 mg/L kinetin and 0.3 mg/L gibberellic acid and subculturing in four-week intervals to the fresh medium of the same composition. Volatile terpene composition was determined by means of capillary gas chromatography. Variations in the terpene profiles were observed between the clones that were classified into two different chemotypes. Moreover, the use of the enantiomers of α-pinene was helpful to distinguish between the different clones. These data warrants further studies in order to compare the terpene composition of in vitro and in vivo plants and to establish the utility of micropropagation techniques to propagate selected chemotypes for industrial purposes.

Enantiomeric distribution of key volatile components in Citrus essential oils

Citrus as many other plants present characteristic distribution of some enantiomers, thus it is often possible to use this parameter for identification, characterization, genuineness, and pharmacological activity assessment. In particular, it is possible to reveal adulteration of different nature, such as addition of synthetic compounds, or natural components of different botanical origin, with drastic changes in the biological and olfactory properties. This study is focused on the evaluation of the enantiomeric excesses of numerous samples of different Citrus species: C. deliciosa Ten., C. limon (L.) Burm., C. bergamia, C. aurantifolia (Christm.) Swing., C. latifolia Tan., C. sinensis (L.) Osbeck, and C. aurantium L. The enantiomeric distribution is determined by direct esGC and, depending on the complexity of the essential oil, by MDGC with a chiral column in the second dimension. The research is focused on the determination of fourteen chiral components which present specific distribution in the essential oils investigated. Particular attention is given to the trend of the enantiomeric distribution during the productive season, so to identify useful parameters for quality assessment also in consideration of the wide range of variability often reported in literature. The components investigated were the following: α-thujene, α-pinene, camphene, β-pinene, sabinene, α-phellandrene, β-phellandrene, limonene, linalool, camphor, citronellal, linalyl acetate, terpinen-4-ol, α-terpineol. The use of MDGC allowed the separation of the enantiomers of camphor and citronellal, otherwise not separated by conventional esGC; however for the separation of the enantiomers of α-pinene it was preferable to use conventional esGC. The MDGC system allowed to determine the enantiomeric distribution of camphene, α- and β-phellandrene in lime essential oil for the first time. The results are discussed in function of seasonal variation and, when possible, in function of the extraction technology, with particular regards to lime oils.

Enantiomeric composition of α-pinene in essential oils of leaves and unripe cones of Juniperus communis L

The leaves and unripe cones of common juniper (Juniperus communis L.) were sampled from 11 habitats across Lithuania. The essential oils of leaves and cones from 110 samples (=trees) each were isolated by hydrodistillation in a European Pharmacopoeia apparatus during two hours. The enantiomers of α-pinene were separated by the chiral-phase capillary GC and identified by matching their retention times to the optically pure analytical standards. The average content, the min-max values and the variation coefficient of (1R)-(+)-α-pinene were 74±1%, 7–92% and 16.4% in leaves and 69±2%, 0–96% and 24.9% in unripe cones, respectively; the average content, the min-max values and the variation coefficient of (1S)-(-)-α-pinene were 26±1%, 8–93% and 45.8% in leaves and 31±2%, 4–100% and 55.7% in unripe cones, respectively. It was established that the most of samples of leaves and unripe cones of the studied J. communis individuals were rich in (1R)-(+)-α-pinene, while (1S)-(-)-α-pinene dominated in 2.7% samples of leaves and 10.9% those of unripe cones only. However, the (1S)-(-)-α-pinene absolutely predominated in leaves of two J. communis individuals. The absolute predomination of the (1R)-(+)-α-pinene was not detected neither in leaves nor in unripe cones.

Biotransformation of α-Pinene to Terpineol by Resting Cell Suspension of Absidia corulea.

Microbial biotransformation of monoterpenes results in the formation of many valuable compounds. Many microorganisms can be used to carry out extremely specific conversions using substrates of low commercial value. Absidia corulea MTCC 1335 was examined for its ability to transform α-Pinene enantiomers. The substrates (-)-α-Pinene and (+)-α-Pinene converted to α-terpineol and isoterpineol, were detected in gas chromatographic analysis. The Biotransformation kinetics of the oxidized products were analysed using GC-MS. With both the substrates the products formed were similar and not much difference in the rate of transformation was observed, suggesting no enantioselectivity of organism towards the substrate.