A stable isotope approach to assessing water loss in fruits and vegetables during storage.

Plant tissue water is the source of oxygen and hydrogen in organic biomatter. Recently, we demonstrated that the stable hydrogen isotope value (δ(2)H) of plant methoxyl groups is a very reliable and easily available archive for the δ(2)H value of this tissue water. Here we show in a model experiment that the δ(2)H values of methoxyl groups remain unchanged after water loss during storage of fruits and vegetables under controlled conditions, while δ(2)H and δ(18)O values of tissue water increase.

A simple rapid method to precisely determine (13)C/(12)C ratios of plant methoxyl groups.

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.

Inter-laboratory comparison of elemental analysis and gas chromatography/combustion/isotope ratio mass spectrometry. II. Delta15N measurements of selected compounds for the development of an isotopic Grob test.

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.

A rapid and precise method for determination of D/H ratios of plant methoxyl groups.

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.

Fungal biotransformation of (+/-)-linalool.

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.

Biosynthesis of monoterpenes and norisoprenoids in raspberry fruits (Rubus idaeus L.): the role of cytosolic mevalonate and plastidial methylerythritol phosphate pathway.

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 c.-292C>T promoter polymorphism increases reticulocyte-type 15-lipoxygenase-1 activity and could be atheroprotective.

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.

Stereoisomeric pattern of lilac aldehyde in Silene latifolia, a plant involved in a nursery pollination system.

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.

Mechanism of wine lactone formation: demonstration of stereoselective cyclization and 1,3-hydride shift.

The cyclization mechanism of (E)-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid to wine lactone under acidic aqueous conditions was investigated using the two stereoselectively deuterium-labeled precursors (2E,6R,7Z)-[8-2H]-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid and (2E,7E)-(+/-)-[8-2H]-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid. A detailed analysis of the generated wine lactone isomers by enantioselective multidimensional gas chromatography (MDGC)/ion trap tandem mass spectrometry demonstrates that the formation of wine lactone proceeds via a nonenzymatic stereoselective cationic cyclization cascade that includes a 1,3-hydride shift. Usually, such mechanisms are features of cyclization reactions that are catalyzed by terpene cyclases.

Intrageneric differences in the four stereoisomers of stenusine in the rove beetle genus, Stenus (Coleoptera, Staphylinidae).

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.

Enantiomer separation on monolithic silica HPLC columns using chemically bonded methylated and methylated/acetylated 6-O-tert-butyldimethylsilylated beta-cyclodextrin.

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.

Linalool and lilac aldehyde/alcohol in flower scents. Electrophysiological detection of lilac aldehyde stereoisomers by a moth.

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.

Biosynthesis of mono- and sesquiterpenes in strawberry fruits and foliage: 2H labeling studies.

The biosynthesis of the monoterpene (S)-linalool and the sesquiterpene trans-(S)-nerolidol in fruits of Fragaria x ananassa Duch. cv. Eros and Florence and of the monoterpene (-)-alpha-pinene in Fragaria vesca was investigated by in vivo feeding experiments with [5,5-2H2]mevalonic acid lactone (d2-MVL) and [5,5-2H2]-1-deoxy-d-xylulose (d2-DOX).

Enantioselective analysis of monoterpenes in different grape varieties during berry ripening using stir bar sorptive extraction- and solid phase extraction-enantioselective-multidimensional gas chromatography-mass spectrometry.

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.

Improved enantioselective analysis of polyunsaturated hydroxy fatty acids in psoriatic skin scales using high-performance liquid chromatography.

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.

Induction of de novo volatile terpene biosynthesis via cytosolic and plastidial pathways by methyl jasmonate in foliage of Vitis vinifera L.

The terpene biosynthesis in leaves of Vitis vinifera L. cv. Morio Muskat was studied using methyl jasmonate to induce defensive responses in vivo.

Comprehensive authentication of (E)-alpha(beta)-ionone from raspberries, using constant flow MDGC-C/P-IRMS and enantio-MDGC-MS.

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.

Biosynthesis of mono- and sesquiterpenes in carrot roots and leaves (Daucus carota L.): metabolic cross talk of cytosolic mevalonate and plastidial methylerythritol phosphate pathways.

The biosynthesis of the monoterpenes terpinolene and myrcene and the sesquiterpene beta-caryophyllene in roots and leaves of two carrot varieties (Daucus carota L. cultivars Bolero and Kazan) were investigated by in vivo feeding experiments with [5,5-2H2]-mevalonic acid lactone (d2-MVL) and [5,5-2H2]-1-deoxy-D-xylulose (d2-DOX). The volatiles of the tissues were extracted by stir bar sorptive extraction and analyzed using thermal desorption-multidimensional gas chromatography-mass spectrometry.

Metabolism of geraniol in grape berry mesocarp of Vitis vinifera L. cv. Scheurebe: demonstration of stereoselective reduction, E/Z-isomerization, oxidation and glycosylation.

The metabolism of deuterium labeled geraniol in grape mesocarp of Vitis vinifera L. cv. Scheurebe was studied by in vivo-feeding experiments.

Enantioselective analysis of free and glycosidically bound monoterpene polyols in Vitis vinifera L. cvs. Morio Muscat and Muscat Ottonel: evidence for an oxidative monoterpene metabolism in grapes.

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.

Biogenetic studies in Syringa vulgaris L.: bioconversion of (18)O(2H)-labeled precursors into lilac aldehydes and lilac alcohols.

Syringa vulgaris L. inflorescences, petals, and chloroplasts, isolated from lilac flower petals, were fed with aqueous solutions of (18)O-labeled linalool and [5,5-(2)H(2)]-deoxy-d-xylose (DOX). The chloroplasts of lilac flower petals were isolated after feeding experiments with labeled precursors.

Simultaneous enantioselective analysis of chiral urinary metabolites in patients with Zellweger syndrome.

Enantio-MDGC-MS analysis with heptakis-(2,3-di-O-methyl-6-O-tert.-butyl-dimethylsilyl)-beta-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.

Multidimensional gas chromatography-mass spectrometry for tracer studies of fatty acid metabolism via stable isotopes in cultured human trophoblast cells.

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.

Synthesis, structure elucidation, and olfactometric analysis of lilac aldehyde and lilac alcohol stereoisomers.

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.