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Heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclo -dextrin proves to be a versatile chiral stationary phase for the direct differentiation of aroma-relevant enantiomers.

Combinations of two or three capillary columns, coated with modified cyclodextrins are used as chiral CGC-separation systems for the direct stereo-differentiation of menthone (1), isomenthone (2), menthol (3), and menthyl-acetate (4), to evaluate their enantiomeric ratios in mentha oils. Optical purity of 1–4 is discussed as an indicator of the natural origin of mint and peppermint oils. Chirale Verbindungen aetherischer Ole, 7. Mitt. : Bewertung von Mentha-Olen durch enantioselektive CGC-Analyse von Monoterpen-Bestandteilen. Kombinationen aus zwei bzw. drei Kapillarsaulen, die mit modifizierten Cyclodextrinphasen belegt sind, werden als chirale Trennsysteme zur direkten Stereodifferenzierung von Menthon (1), Isomenthon (2), Menthol (3) und Menthylacetat (4) beschrieben und deren Enantiomerenverhaltnisse in Mentha-Olen bestimmt. Die optische Reinheit der Monoterpene 1–4 wird als Indikator fur die naturliche Herkunft von Minz- und Pfefferminzolen diskutiert.

Stable isotope ratios of individual plant components have become a valuable tool for the determination of the geographical origin and authenticity of foodstuff. A recently published method with considerable potential in this context is the measurement of the deuterium/hydrogen (D/H) isotope ratios of plant matter methoxyl groups. The method entailed cleavage of methyl ethers or esters with hydriodic acid (HI) to form gaseous methyl iodide (CH(3)I) and then measurement of the delta(2)H value of this gas. Here, as a follow up to a previous study, we describe a method for the rapid and precise delta(13)C analysis of plant matter methoxyl groups using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Conditions for sample preparation were investigated for isotope discrimination effects, the GC conditions optimized, the reproducibility of the measurement of standards undertaken, and the precision of the method defined. The reproducibility of the delta(13)C value determined for a CH(3)I standard on 20 consecutive measurements was found to be 0.17 per thousand. The method was also tested on four methoxyl-rich plant components: vanillin, lignin, wood and pectin. The analytical precision obtained, expressed as the average standard deviation, for these compounds was found to be better than 0.13 per thousand. The described procedure which is simple and rapid, allowing preparation and analysis of a sample within 1 h, produces accurate and reproducible isotopic measurements. We suggest that this validated delta(13)C method when employed together with the recently published delta(2)H method for two-dimensional stable isotope studies of organic matter containing methoxyl groups will be of considerable value, e.g. for proving the authenticity of foodstuff.

An inter-laboratory exercise was carried out by a consortium of five European laboratories to establish a set of compounds, suitable for calibrating gas chromatography/combustion/isotope ratio mass spectrometry (GC-C-IRMS) devices, to be used as isotopic reference materials for hydrogen, carbon, nitrogen and oxygen stable isotope measurements. The set of compounds was chosen with the aim of developing a mixture of reference materials to be used in analytical protocols to check for food and beverage authentication. The exercise was organized in several steps to achieve the certification level: the first step consisted of the a priori selection of chemical compounds on the basis of the scientific literature and successive GC tests to set the analytical conditions for each single compound and the mixture. After elimination of the compounds that turned out to be unsuitable in a multi-compound mixture, some additional oxygen- and nitrogen-containing substances were added to complete the range of calibration isotopes. The results of delta(13)C determinations for the entire set of reference compounds have previously been published, while the deltaD and delta(18)O determinations were unsuccessful and after statistical analysis of the data the results did not reach the level required for certification. In the present paper we present the results of an inter-laboratory exercise to identify and test the set of nitrogen-containing compounds present in the mixture developed for use as reference materials for the validation of GC-C-IRMS analyses in individual laboratories.

Selectively alkylated and acylated cyclodextrin derivatives are suitable stationary phases for capillary GC. To obtain a closer insight into the separation mechanism, an inverse substituted cyclodextrin derivative was synthesized and characterized, and its chiral selectivity was compared with a traditionally substituted and characterized cyclodextrin. The influence of a polar group in the cyclodextrin molecule on the enantioselectivity for γ-/δ-lactones is shown with a new, diacylated, cyclodextrin derivative.

Using perethylated β-cyclodextrin as a chiral stationary phase the alcohols 2-methyl-1-butanol (1), -pentanol (2), -hexanol (3) and 2-ethyl-1-hexanol (4), the free carboxylic acids 2-methyl-butanoic (5), -pentanoic (6), -hexanoic (7) and 2-ethylhexanoic (8) as well as the esters methyl and ethyl 2-methylbutanote (9, 10) are resolved into their mirror images without derivatization. Chiral capillary gas chromatography was used to determine the enantiomeric distribution of the 2-methylbutanoates 9 and 10 in pineapples and 15 apple varieties, using extractive and dynamic headspace methods, respectively.

Thecis-6-γ-dodecenolactone is the major monounsaturated γ-lactone produced by a filamentous fungus,Fusarium poae. The two enantiomeric forms of this compound were successfully separated by column gas chromatography, on a fused silica capillary column coated with a modifiedα-cyclodextrin orβ-cyclodextrin phase, and by HPLC, on a Chiraspher column. Elucidation of the configuration of each enantiomer was realized by the interpretation of the1H-NMR spectra of the Moshers' esters formed with the corresponding 4-hy-droxyalkenoic acid esters of this lactone. An analysis of an extract obtained from a culture ofF. poae in a liquid malt broth showed that the (R)-enantiomer was highly predominant (>99%). The odour of each pure enantiomer was assessed by sniffing the column effluent: the detection threshold calculated for the (S)-enantiomer is 2–3 times lower than that of the (R)-form (3 and 7 pg, respectively, of injected compound). This result was confirmed by a sensory analysis of each enantiomer diluted in water at a level of 1.3 μg/ml. The odour of the (S)-en-antiomer was significantly described as more intense than that of the (R)-form, but no sensory difference was found in the odour quality, which was described as flowery, fruity, coconut-, peach- and apricot-like.

The enantiomeric separation of δ-lactones up to the long-chain compounds δ-trideca-(δ-C 13 -) and δ-tetradeca-(δ-C 14 -)-lactone is demonstrated. By means of optically pure references, the order of elution S(I), R(II) was determined for the important flavour compounds δ-octa-, δ-deca-, and δ-dodecalactone. Analysis of the steam distillate of some dairy products (milk, cream, butter), of margarine and of coconut has been carried out, in order to yield the enantiomeric distribution of C 8 -, C 10 - and C 12 -δ-lactones by HRGC and multidimensional gas chromatography. Characteristic and product-specific ratios of δ-lactone enantiomers are detected

Using enantioselective MDGC the enantiomeric distribution of alkan-(alken-)2-yl-acetates from bananas is achieved. After simple acetylation their corresponding alcohols 2-pentanol, 2-hexanol, 2-heptanol an d (Z)-4-hepten-2-ol respectively are also exactly stereodifferentiated by the same method. All compounds investigated -esters as well as alcohols -exhibit a remarkable excess of the (S)-enantiomers.

The synthesis of several 2-alkoxy-5-alkyl-tetrahydrofurans is of interest in our investigations of structure–function relationships of chiral flavour compounds. For the preparation of the enantiomeric acetals the unambiguous configurational assignment of the cis and trans series of these compounds is indispensable. By means of crystalline acetal derivatives the absolute structure of a model compound in the cis and the trans configuration is revealed by X-ray measurement and correlated with the corresponding cis and trans configurated aroma compounds. The first complete structure elucidation of the class of 2-alkoxy-5-alkyltetrahydrofurans has been carried out.

Racemic 2-alkylbranched acids are transformed to diastereomeric derivatives with (S)-2-hydroxy-3-phenylpropionic acid-N-methylamide or (S)-(−)-1-phenylethylamineand separated by liquid chromatography to pure diasterecisomers, which are subsequently hydrolyzed to yield optically pure acids. Enantiomeric alcohols are generated by LiAlH4-reduction of the corresponding acids, esters are synthesized by different methods. The odour impression of the enantiomeric compounds is investigated.

Stable hydrogen isotope ratio measurements of specific plant components are increasingly used in numerous fields of research, including sample origin verification and climate research. A recently suggested method with considerable potential in this context is the D/H isotope ratio (delta(2)H value) analysis of plant matter methoxyl groups. The method entails ether or ester cleavage with hydriodic acid (HI) to form the gaseous compound methyl iodide (CH(3)I) and measurement of the delta(2)H value of this gas. Here we describe a method for the rapid and precise delta(2)H analysis of plant matter methoxyl groups using gas chromatography/pyrolysis/isotope ratio mass spectrometry (GC/P/IRMS). The conditions for sample preparation were investigated for isotope discrimination effects, the GC conditions were optimized, the reproducibility of the measurement of standards was studied, and the precision of the method was defined. The reproducibility of delta(2)H values determined for a CH(3)I standard on 20 consecutive measurements was found to be 2 per thousand. The method was also tested on four methoxyl-rich plant components: vanillin, lignin, wood and pectin. The analytical precision obtained, when expressed as the average standard deviation for these compounds, was better than 1.6 per thousand. The described method is rapid, allowing preparation and analysis of a sample within 1 h, and produces accurate and reproducible isotopic measurements.

The biotransformation of (+/-)-linalool was investigated by screening 19 fungi. Product accumulation was enhanced by substrate feeding and, for the first time, lilac aldehydes and lilac alcohols were identified as fungal biotransformation byproduct using SPME-GC-MS headspace analysis. Aspergillus niger DSM 821, Botrytis cinerea 5901/02, and B. cinerea 02/FBII/2.1 produced different isomers of lilac aldehyde and lilac alcohol from linalool via 8-hydroxylinalool as postulated intermediate. Linalool oxides and 8-hydroxylinalool were the major products of fungal (+/-)-linalool biotransformations. Furanoid trans-(2 R,5 R)- and cis-(2 S,5 R)-linalool oxide as well as pyranoid trans-(2 R,5 S)- and cis-(2 S, 5 S)-linalool oxide were identified as the main stereoisomers with (3 S,6 S)-6,7-epoxylinalool and (3 R,6 S)-6,7-epoxylinalool as postulated key intermediates of fungal (+/-)-linalool oxyfunctionalization, respectively. With a conversion yield close to 100% and a productivity of 120 mg/L.day linalool oxides, Corynespora cassiicola DSM 62485 was identified as a novel highly stereoselective linalool transforming biocatalyst showing the highest productivity reported so far.

The enantiomers of α-pinene, β-pinene and limonene were directly determined in complex matrices by multidimensional gas chromatography using a non-chiral-chiral column combination. Essential oils, used for the preparation of perfumes and cosmetics, and commercially available perfumery products were analysed without sample clean-up. The enantiomeric distribution of the monoterpenes investigated allows a quality control of perfumes, a validation of essential oils as well as a differentiation of their natural or artificial origin.

La resolution enantioselective des γ-lactones sur la phase stationnaire alkyl-acetyl α-cyclodextrine/OV1701 OH utilisee necessite des conditions chromatographiques inhabituelles

La quantite d'acetate de linalyle (A) dans l'huile essentielle de Lavandula angustifolie est un critere de qualite. Description et discussion de la purete optique de A

2-Alkyl-substituted 4-methyl(4,5-dimethyl)-1,3-dioxolanes are synthesized by the cyclization of propan-1,2-diol and butan-2,3-diol with “Strecker aldehydes” as the carbonyl compounds. The stereo-isomeric 1,3-dioxolanes are separated by micro-preparative multidimensional gas chromatography and their structures assigned using1H-NMR spectroscopy (300 MHz). These references with definite stereochemistry are required for reliable interpretation of their chromatographic behaviour with Ni(II)-bis-[3-heptafluorobutanoyl-(1R,2S)-pinanoate] and Ni(II)-bis-[heptafluorobutanoyl]-(1R)-camphorate] respectively, as the chiral stationary phases.

Chiral γ-lactones from the raw flavor extract of strawberries and of some commercially available fruit-containing foods and beverages were directly stereoanalyzed by multidimensional gas chromatography (MDGC), employing heart-cutting techniques from DB 1701 as the preseparation column onto heptakis(3-O-acetyl-2,6-di-O-pentyl)β-cyclodextrin as the chiral stationary phase

The aim of this work was to determine the enantiomeric composition of C 6 -C 12 γ-lactones in these fruits. The direct stereodifferentiation of C 9 -C 12 γ-lactones has already been carried out by Mosandl and co-workers 10-13 by multi-dimensional (MD) gas chromatography (GC) 14,15 on different commercially available fruit nectars

The biosynthesis of the monoterpenes (-)-alpha-pinene, linalool, and the norisoprenoids alpha- and beta-ionone in raspberry fruits (rubus idaeus L.) was investigated by in vivo feeding experiments with [5,5-(2)H2]-mevalonic acid lactone and [5,5-(2)H2]-1-deoxy-D-xylulose. The volatile compounds were extracted by stirbar sorptive extraction and analyzed using thermal desorption-multidimensional gas chromatography-mass spectrometry (TD-enantio-MDGC-MS). The feeding experiments demonstrate that (-)-alpha-pinene and (S)-linalool are exclusively synthesized via the cytosolic mevalonic acid pathway. In contrast, (2)H-labeled (R)-(E)-alpha-ionone and (2)H-labeled (E)-beta-ionone are detectable after application of d2-1-deoxy-D-xylulose and d2-mevalonic acid lactone, respectively. However, (R)-linalool reveals no incorporation of either one of the fed precursors, even though this enantiomer is detectable in the fruit tissue.

This study was directed towards investigating suitable compounds to be used as stable isotope reference materials for gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) calibration. Several compounds were selected from those used in the 'Grob-test' mixture. Oxygen- and nitrogen-containing substances were added to these compounds to allow the mixture to be used as a possible multi-isotopic calibration tool for 2H/1H, 13C/12C, 15N/14N and 18O/16O ratio determinations. In this paper we present the results of delta13C measurements performed by the consortium of the five laboratories taking part in this inter-calibration exercise. All the compounds were individually assessed for homogeneity, short-term stability and long-term stability by means of EA-IRMS, as required by the bureau communitaire de reference (BCR) Guide for Production of Certified Reference Materials. The results were compared then with the GC-C-IRMS measurements using both polar and non-polar columns, and the final mixture of selected compounds underwent a further certification exercise assessing limits of accuracy and reproducibility under specified GC-C-IRMS conditions.

Background Reticulocyte-type 15-lipoxygenase-1 (ALOX15) has anti-inflammatory and inflammatory effects and is implicated in the development of asthma, arthritis and atherosclerosis. Previously, we screened the human ALOX15 gene for variations because genetic variability in ALOX15 might influence these diseases. We found a C>T substitution at position c.-292 in the ALOX15 promoter that created a novel binding site for the transcription factor SPI1 and increased ALOX15 mRNA levels in monocytes from c.-292CT heterozygous volunteers. Methods To test whether the higher mRNA levels led to higher ALOX15 activity, we performed an activity assay and measured the arachidonic acid metabolite 15(S)-hydroxy-eicosatetraenoic acid [15(S)-HETE] by HPLC analysis. To test whether this polymorphism was associated with coronary artery disease (CAD), we investigated its association in a case-control study involving 498 Caucasians. Results The c.-292C>T polymorphism was associated with higher enzyme activity in heterozygous carriers. Intriguingly, this polymorphism also showed a tendency to be protective against atherosclerosis. Conclusions These results suggest that increased ALOX15 activity may attenuate inflammation, which could be caused by an increase in 15(S)-HETE and eventually by its metabolites, the lipoxins.

2-Methylbutanoic acid, an aroma compound of high economic interest, was synthesised using Gluconobacter species for bioconversion. The main focus was on enantioselective effects during metabolism. A preference for the (S)-enantiomer was observed when the microorganisms were fed with 2-methylbutanol of known enantiomeric ratios.

The on-line coupling of gas chromatography and isotope ratio mass spectrometry via a pyrolysis interface (GC-pyrolysis-IRMS, GC-P-IRMS) allows the simultaneous determination of δ13C and δ18O values for organic compounds. On the basis of illustrative investigations of vanillin from different origins, the scope and limitations of the new method are discussed.

The monoterpene lilac aldehyde is found in floral scent of several plants species, among them Silene latifolia. This plant is involved in a nursery pollination system, because a noctuid moth, Hadena bicruris, is not only pollinator but also seed predator. Lilac aldehyde is the key floral scent compound of S. latifolia for attracting Hadena. This monoterpene has three stereogenic centers, and eight different isomers are possible. Here, we analysed the ratio of lilac aldehyde isomers from plants originating from 18 different populations of S. latifolia using enantioselective multidimensional GC-MS (enantio-MDGC-MS), and compared resulting variability with variability found in total scent emitted by specimen under study. Though variability in total emitted scent was high, ratio of lilac aldehyde isomers was a more conservative trait. There was no correlation between the ratio of lilac aldehyde isomers and the total emitted floral scent pattern. Both, ratio of stereoisomers and total emitted scent were independent from the geographic origin of the plants. In conclusion, the ratio of lilac aldehyde stereoisomers in S. latifolia is a reliable trait, and may used by the nursery pollinator H. bicruris for host-plant detection.

A new 2,3-methylated 3*-monoacetylated 6-O-tert-butyldimethylsilylated beta-CD derivative was synthesized and chemically bonded onto aminopropyl derivatized monolithic silica HPLC columns. In this CD derivative, only one of seven methyl groups in 3-position was substituted by an acetyl group. Its applicability as a chiral stationary phase for HPLC was tested and compared with exclusively 2,3-methylated 6-O-tert-butyldimethylsilylated beta-CD immobilized onto aminopropyl-modified monoliths. Thirty-two chiral compounds from different chemical classes and different functionalities were tested under RP conditions. Fourteen compounds were resolved into their enantiomers by methylated 6-O-tert-butyldimethylsilylated beta-CD. By use of methylated/acetylated 6-O-tert-butyldimethylsilylated beta-CD as the chiral stationary phase 7 analytes were successfully stereodifferentiated.

Most species of the rove beetle genus Stenus employ the spreading alkaloid stenusine as an escape mechanism on water surfaces. In the case of danger, they emit stenusine from their pygidial glands, and it propels them over the water very quickly. Stenusine is a chiral molecule with four stereoisomers: (2'R,3R)-, (2'S,3R)-, (2'S,3S)-, and (2'R,3S)-stenusine. The percentile ratio of these four isomers is only known for the most common species of the genus: Stenus comma. With the intention of determining the stereoisomer ratios of five additional species from the two subgenera, Stenus and Hypostenus, we used GC/mass spectrometry measurements with a chiral phase. The results showed that the ratio differs among the genus. These findings can be a basis for chemotaxonomy. It is also possible that the biological function of stenusine, e.g., as antibiotic or fungicide, varies with changing stereoisomer composition.

Nineteen different fungi were screened to test their capability to convert (±)-linalool into lilac aldehydes and lilac alcohols. Solid phase microextraction (SPME) in combination with GC-MS was used to identify the target compounds by comparing retention times and mass spectra with chemically synthesised standards. Most of the strains showed specific and complex product spectra, often with linalool oxides and dihydrolinalool as major metabolites. Aspergillus niger DSM 821, Botrytis cinerea 5901/02 and Botrytis cinerea 02/FB II/2.1 generated the desired lilac fragrance compounds as metabolic by-products.

The stereoisomers of linalool and lilac aldehyde/alcohol were determined in the flower scent of 15 plant species using enantioselective multidimensional gas chromatography/mass spectrometry (enantio-MDGC/MS). Both linalool and all 8 stereoisomers of lilac alcohol and lilac aldehyde were detected, and there was a species-specific pattern. Single stereoisomers were collected by micropreparative-enantio-MDGC and were electrophysiologically tested on antennae of the noctuid moth Hadena bicruris, a species known to rely on lilac aldehyde for finding its host plant. The moth responded to all 8 stereoisomers, though only four stereoisomers were found in the scent of its host plant. The moth was less sensitive to some isomers than to others.

The stereoisomeric ratios of various genuine metabolites of linalool (furanoid and pyranoid linalool oxides, hotrienol) and citronellol (cis- and trans-rose oxide) were determined in grape berries by means of enantioselective-multidimensional gas chromatography-mass spectrometry. Stereoisomers of the metabolites could be separated on a chiral column with a modified cyclodextrin as stationary phase. The detailed stereoselective analysis of the furanoid and pyranoid linalool oxides in the cv. Morio-Muskat during berry ripening is giving evidence that furanoid linalool oxides are generated via two different reaction pathways. Additionally, stereoselective analysis of rose oxide in different varieties that have attained commercial maturity has been performed demonstrating that cis-(2S,4R)-rose oxide is the main stereoisomer in all varieties. (3S)-Hotrienol was the main stereoisomer in all varieties with enantiomeric purities that were always higher than 90%.

A new coupling system of GC-GC, connected via a Multi Column Switching Device MCS2 for measuring isotope ratios, is introduced. By means of several standard substances the precise and accurate measurement of isotopic values is proved. First applications concerning the authentication of raspberry aroma compounds are established. Consequently, the combination of constant flow multidimensional gas chromatography-combustion/pyrolysis-isotope ratio mass spectrometry (MDGC-C/P-IRMS) is applied to the authenticity assessment of (E)-alpha(beta)-ionone from six different raspberry cultivars. Furthermore, 12 commercially available raspberry products and samples of (E)-alpha(beta)-ionone, some declared to be natural, are investigated. delta(2)Eta(V)(-)(SMOW) and delta(13)C(V)(-)(PDB) values of (E)-alpha(beta)-ionone are determined, and characteristic authenticity ranges were concluded from raspberries by correlation of both delta(2)Eta(V)(-)(SMOW) and delta(13)C( V)(-)(PDB) values. The results are correlated with the determination of enantiomeric purities of (E)-alpha-ionone, using stir bar sorptive extraction enantio-multidimensional gas chromatography mass spectrometry (SBSE-enantio-MDGC-MS).

(1996). Elution Order of the Furanoid Linalool Oxides on Common Gas Chromatographic Phases and Modified Cyclodextrin Phases. Journal of Essential Oil Research: Vol. 8, No. 4, pp. 339-341.

Enantioselective analysis is used as a valuable tool for determining the biological origin of chiral derivatives of arachidonic, 11,14-eicosadienoic and linoleic acid in psoriatic skin scales and for clarifying their role in pathogenesis. This paper reports on a simple and rapid enantioselective determination (without any derivatization) of the fatty acid derivatives 13(R,S)-hydroxyoctadecadienoic acid [13(R,S)-HODE], 9(R,S)-hydroxyoctadecadienoic acid [9(R,S)-HODE] and 12(R,S)-hydroxyeicosatetraenoic acid [12(R,S)-HETE], using high-performance liquid chromatography (HPLC) with Chiralpak® AD as the chiral selector and electrospray ionisation mass spectrometry (ESI-MS). The enantiomeric distribution of 12-HETE, 9-HODE and 13-HODE in psoriatic skin scales of untreated patients (untreated during the last 4 weeks before sampling) was evaluated in comparison to psoriatic skin scales of patients underlying systemic treatment. The enantiomeric distribution of 12-HETE and 9-HODE showed no remarkable differences, whilst samples of patients under systemic treatment exhibited a lower predominance of 13(S)-HODE than samples of untreated patients. Furthermore, the effect of UVB phototherapy on the enantiomeric distribution of 12-HETE, 9-HODE and 13-HODE was studied and a semiquantitation of these compounds in psoriatic skin scales performed. The detected amounts of 9-HODE in samples of untreated patients were remarkably lower than those in samples of patients underlying systemic treatment. In the case of UVB phototherapy, no influence on the enantiomeric distribution could be observed.

The metabolism of deuterium labeled geraniol in grape mesocarp of Vitis vinifera L. cv. Scheurebe was studied by in vivo-feeding experiments. Stereoselective reduction to (S)-citronellol, E/Z-isomerization to nerol, oxidation to neral/geranial and glycosylation of the corresponding monoterpene alcohols could be demonstrated. Time course studies including the determination of conversion rates revealed that the activity of these secondary transformations of monoterpenes is dependent on the ripening stage and can be distinguished from the development of the primary monoterpene synthase activities by the sharp increase at the end of the ripening period. The stereoselective biosynthesis of the potent odorant cis-(2S,4R)-rose oxide from labeled geraniol in grape berry mesocarp is demonstrated as well. Since (S)-citronellol is the precursor of cis-(2S,4R)-rose oxide it can be concluded that especially the last part of the ripening period is important for the generation of this potent odorant. This finding confirms the conclusion that a higher concentration of flavor compounds could be established in the berries by leaving the fruit on the vine for extended periods.

The enantiomeric ratios of various free and glycosidically bound monoterpene polyols in musts of the aromatic grapes Vitis vinifera L. cvs. Morio Muscat and Muscat Ottonel were determined by means of enantioselective multidimensional gas chromatography-mass spectrometry. Reference compounds of defined stereochemistry were synthesized and permitted the unequivocal determination of the elution order of the target compounds on chiral columns with modified cyclodextrins as stationary phases. It could be shown for the first time that the linalool-derived polyol 3,7-dimethylocta-1,7-dien-3,6-diol occurs predominately as the (3S,6S)-configured stereoisomer, providing evidence that this compound is generated by an enzymatic process in grape berries. The involvement of a cytochrome P450 monooxygenase in the oxidative metabolism of monoterpenes in grapes is dicussed.

Enantio-MDGC–MS analysis with heptakis-(2,3-di- O -methyl-6- O - tert. -butyl-dimethylsilyl)-β-cyclodextrin as the chiral main column is a powerful tool for the separation of chiral compounds. This paper reports on the simultaneous stereodifferentiation of 2-hydroxyisocaproic acid (HICA), 3-methyladipic acid (3-MA), 2-hydroxyglutaric acid (2-HG), 3-(4-hydroxyphenyl)-lactic acid (HPLA), 2-hydroxysebacic acid (2-HS) and 3-hydroxysebacic acid (3-HS) in a single chromatographic run. These chiral urinary metabolites are useful in the diagnosis of peroxisomal diseases such as Zellweger syndrome (ZS). In this investigation, urine samples from nine patients with ZS were analysed in order to reveal the enantiomeric ratio of these chiral metabolites. The stereodifferentiation of the analysed chiral compounds may provide important information on their biochemical origin.

The determination of placental fatty acid metabolism using stable isotope-labeled tracers was investigated in the human placental choriocarcinoma (JAR) cell line. Stable isotope incorporation was measured by MDGC–MS. The cultured trophoblast cells incorporated and metabolized the essential fatty acids to long-chain polyunsaturated fatty acids. The described method enables the detection of a low Δ 6 -desaturase activity in this human placental cell line. The developed MDGC–MS method allows the assessment of long-chain polyunsaturated fatty acid biosynthesis in cultured cells with high sensitivity and selectivity. In this respect, tracer studies with MDGC–MS will be a powerful tool to clarify the significance of placental fatty acid metabolism.

Structure elucidation of the lilac aldehyde and lilac alcohol stereoisomers was ascertained by (1)H nuclear magnetic resonance (NMR) spectroscopy, including intramolecular nuclear Overhauser effects of the separated diastereoisomers and anisotropic effects of the diastereomeric 2-phenylpropionyl ester, and (1)H, (1)H COSY NMR spectroscopy of synthesized (5'R)-configured stereoisomers, synthesized from (R)-linalool. Direct stereodifferentiation of the eight stereoisomers of lilac aldehyde and lilac alcohol, respectively, has been achieved, using enantioselective capillary GC. The elution order of the isomers was deduced from the chromatographic behavior of the (5'R)-configured diastereoisomers. Additionally, the odor thresholds of lilac aldehyde and lilac alcohol stereoisomers are reported.

The chiral metabolite 2-hydroxysebacic acid (2-HS) is considered to be an important diagnostic marker for peroxisomal disorders. The pathway of formation of 2-HS, excreted in increased amounts in patients with peroxisomal diseases, is not absolutely clear. Moreover, there is no information about the enantiomeric distribution of 2-HS in human urine. Here, we describe the stereodifferentiation of 2-HS in urine samples of nine patients with Zellweger syndrome (ZS), and for the first time in urine samples of premature infants fed a medium-chain triglyceride (MCT)-containing diet. Using enantioselective multidimensional gas chromatography-mass spectrometry, an increased excretion of 2R-HS was observed in all investigated ZS patients. 2-HS was also present in urine samples of premature infants fed MCT. Analogously to the ZS patients, a dominant 2R-HS excretion in the urine samples of the premature infants was identified. The formation of 2-HS is expected to result from the same or similar pathways as described for ZS patients. Additionally, we determined the absolute configuration of urinary 3-hydroxysebacic acid (3-HS) in the cases investigated. The enantioselective analysis provides further information for the diagnosis and treatment of patients with impaired peroxisomal fatty acid oxidation. Further insight into the metabolic origin and the biochemical pathway leading to these urinary metabolites is provided.

The enantiomeric distribution of 3-mercaptohexanol (1) and 3-methylthiohexanol (2) in yellow and purple passion fruits was determined by capillary gas chromatography (GC) using two different chiral stationary phases and a flame photometric detector. The results were confirmed by enantioselective capillary GC combined with mass spectrometric detection. 1 shows an enrichment of the (S)-enantiomer, but the enantiomeric purity varies in a wide range. Irrespective from the enantiomeric distribution of 1, 2 was detected with high enantiomeric purity in favour of the (S)-enantiomer. Using the method presented the addition of synthetic, racemic 2 is easily detected

The biogenetic origin of the isoprenoid building blocks of the sesquiterpene germacrene D was studied in Solidago canadensis. Feeding experiments were carried out with 1-[5,5-D(2)]deoxy-D-xylulose-5-phosphate (D(2)-DOXP), [5-13C]mevalonolactone (13C-MVL) and [1-13C]-D-glucose. The hydrodistillate of a cut shoot fed with D(2)-DOXP was investigated by enantio-MDGC-MS and the volatile fraction of a shoot supplied with 13C-MVL was examined by GC-C-IRMS. The incorporation of [1-13C]-D-glucose was analyzed by quantitative 13C NMR spectroscopy after isolation of germacrene D from the essential oil. Our labeling studies revealed that the biosynthesis of the C-15 skeleton of sesquiterpene germacrene D in Solidago canadensis proceeds predominantly via the methylerythritol phosphate pathway.

Gas chromatography/pyrolysis/isotope ratio mass spectrometry (GC/P/IRMS) is a relatively new method for on-line determination of (2)H/(1)H isotope ratios. The influence of different parameters on the (2)H/(1)H isotope ratios obtained in GC/P/IRMS has been thoroughly studied using several flavor compounds, such as 5-nonanone, linalool, menthol, linalyl acetate and 4-decanolide. The requirement of "conditioning" the pyrolysis reactor to obtain reliable delta(2)H(V-SMOW) values is discussed. Furthermore, the influence of the carrier gas flow of the gas chromatograph on the completeness of pyrolysis and subsequently on the delta(2)H(V-SMOW) values is investigated in detail. The linear range of the compounds investigated is determined. The results show that calibrating the GC/P/IRMS system with secondary standard substances is absolutely necessary in order to obtain reliable delta(2)H(V-SMOW) values. In view of interlaboratory comparability, validation procedures are recommended.