Uwe Hener

Liposome-incorporated DHA increases neuronal survival by enhancing non-amyloidogenic APP processing.

The fluidity of neuronal membranes plays a pivotal role in brain aging and neurodegeneration. In this study, we investigated the role of the omega-3 fatty acid docosahexaenoic acid (DHA) in modulation of membrane fluidity, APP processing, and protection from cytotoxic stress. To this end, we applied unilamellar transfer liposomes, which provided protection from oxidation and effective incorporation of DHA into cell membranes. Liposomes transferring docosanoic acid (DA), the completely saturated form of DHA, to the cell cultures served as controls. In HEK-APP cells, DHA significantly increased membrane fluidity and non-amyloidogenic processing of APP, leading to enhanced secretion of sAPPα. This enhanced secretion of sAPPα was associated with substantial protection against apoptosis induced by ER Ca(2+) store depletion. sAPPα-containing supernatants obtained from HEK-APP cells exerted similar protective effects as DHA in neuronal PC12 cells and HEK293 control cells. Correlating to further increased sAPPα levels, supernatants obtained from DHA-treated HEK-APP cells enhanced protection, whereas supernatants obtained from DHA-treated HEK293 control cells did not inhibit apoptosis, likely due to the low expression of endogenous APP and negligible sAPPα secretion in these cells. Further experiments with the small molecule inhibitors LY294002 and SP600125 indicated that sAPPα-induced cytoprotection relied on activation of the anti-apoptotic PI3K/Akt pathway and inhibition of the stress-triggered JNK signaling pathway in PC12 cells. Our data suggest that liposomal DHA is able to restore or maintain physiological membrane properties, which are required for neuroprotective sAPPα secretion and autocrine modulation of neuronal survival.

Multidimensional Gas Chromatography Coupled On‐Line with Isotope Ratio Mass Spectrometry (MDGC‐IRMS): Progress in the Analytical Authentication of Genuine Flavor Components

Multidimensional gas chromatography coupled on-line with isotope ratio mass spectrometry (MDGC-IRMS) is presented as a powerful method for origin-specific analysis. Scope and limitations of this sophisticated coupling technique are discussed with regard to accuracy and precision.

Comprehensive cGC-IRMS analysis in the authenticity control of flavours and essential oils

ZusammenfassungDieδ13CPDB-Werte von neun Aromakomponenten aus fünf unterschiedlichen Zitronenölen werden mittels GC-IRMS bestimmt. Durch die Wahl eines internen Isotopenstandards (i-IST) werden Isotopeneffekte während der CO2-Fixierung (in der Photosynthese) eliminiert und die zwischen den einzelnen Substanzen auftretenden Unterschiede im13C/12C-Verhältnis auf enzymatische Einflüsse des Sekundärstoffwechsels begrenzt. Mit Nerylacetat als i-IST lassen sich fruchtspezifischeδ13C-Werte von Neral bzw. Geranial mit hoher Genauigkeit bestimmen und zur Authentizitätskontrolle von Zitronenölen heranziehen.SummaryTheδ13CPDB values of nine flavour compounds from five different lemon oils were determined using gas chromatography-isotope ratio mass spectrometry. By definition of a suitable internal isotopic standard (i-IST), the influence of CO2 fixation during photosynthesis is eliminated. The isotopic effects among genuine monoterpenes are, therefore, limited to the influence of enzymatic reactions during secondary biogenetic pathways. Calculating versus nerylacetate as an i-IST yields fruit-specific (δ13C values for neral and geranial with low standard deviation and seems to be suitable for authenticity control of lemon oils.

Stereodifferentiation of some chiral monoterpenes using multidimensional gas chromatography

SummaryHeptakis (2,3,6-tri-O-alkyl)-β-cyclodextrins are used as chiral stationary phases for the resolution of α-pinene (1), β-pinene (2), limonene (3), α-terpineol (4), linalool (5) and the furanoid cis/trans linalool oxides (6) by chirospecific CGC-analysis. The first investigations on the direct chirality evaluation of the monoterpenoid grape and wine flavour compounds 4–6 are reported using enantioselective multidimensional gas chromatography (MDGC) and chiral main columns, coated with peralkylated β-cyclodextrins. The fresh grape juice, the corresponding must, the young and the bottle maturated wine of muscat cultivars are investigated.

Analytische und technologische Einflüsse auf das13C/12C-Isotopenverhältnis von Orangenöl-Komponenten

The influence of Chromatographic and technological procedures on the13C-isotope value of flavour compounds from orange oils was investigated. In order to avoid misinterpretations of isotopic data, quantitative yields during sample clean-up must be ascertained. Ordinary as well as deterpenated orange oils were not influenced by the technological processing. In the case of special products containing single compounds concentrated up to more than 70%, a shift in the13C/12C-isotope ratio was detectable.ZusammenfassungDer Einfluß chromatographischer und technologischer Verfahren auf den13C-Isotopengehalt aromarelevanter Substanzen in Orangenölen wird untersucht. Um Fehlinterpretationen von Isotopendaten auszuschließen, muß eine effektive, verlustfreie Probenaufbereitung sichergestellt werden. Während bei der Verarbeitung einfacher sowie terpenarmer (entterpenisierter) Orangenöle keine Isotopendiskriminierung auftritt, sind bei Spezialprodukten, bei denen einzelne Substanzen Konzentrationen von >70% erreichen, Abweichungen des13C/12C-Isotopenverhältnisses feststellbar.

Analytische Differenzierung zwischen natürlich gewachsenen, fermentativ erzeugten und synthetischen (naturidentischen) Aromastoffen

SummaryWith regard to the analytical differentiation between naturally grown fermentatively produced and synthetic (nature-identical) arome compounds by GC-C-IRMS, simple and practicable methods without any isotope fractionation are essential for efficient enrichment of minor flavour compounds from citrus oils. Octanal, nonanal, decanal, dodecanal, neral and geranial from different orange oils and commercially available products, labelled “natural” or “nature-identical” have been investigated. The13C/12C ratios were evaluated in a narrow range of variation and allowed the differentiation of synthetic nonanal, decanal and dodecanal from their natural analogues.ZusammenfassungIm Hinblick auf die analytische Differenzierung zwischen natürlich gewachsenen, fermentativ erzeugten und synthetischen (naturidentischen) Aromastoffen mittels GC-C-IRMS-Analyse ist es erforderlich, aromarelevante Minorkomponenten mit einfachen, praxisnahen Methoden ohne Isotopendiskriminierung anzureichern. Exemplarisch werden dieδ13CPDB-Werte der Aldehyde Octanal, Nonanal, Decanal, Dodecanal sowie Neral und Geranial unterschiedlicher Handelsqualitäten („natürlich“, „naturidentisch“) und in verschiedenen Orangenölen bestimmt. Für die Alkanale wird ein eng begrenzter natürlicher Schwankungsbereich des13C/12C-Isotopenverhältnisses festgestellt. Nonanal, Decanal und Dodecanal der Handelsqualität „naturidentisch“ sind von ihren natürlichen Analogen aus Orangen (bzw. Orangenölen) klar zu unterscheiden.

Stereoisomere Aromastoffe@@@Stereoisomeric flavour compounds: XLVII. Direkte chirospezifische HRGC-Analyse natrlicher ?-Lactone@@@XLVII. Direct chirospecific HRGC-analysis of natural ?-lactones

Summary5-Alkylatedδ-lactones are well known flavour compounds in animal fats and also some special kinds of fruit. Recently, the first direct stereo-differentiation of chiralδ-lactones was reported using Oktakis(3-O-butyryl-2,6-di-O-pentyl)-γ-cyclodextrin as the chiral stationary phase [4]. The enantiomeric separation ofδ-lactones up to the long-chain compoundsδ-trideca-(δ-C13−) andδ-tetradeca-(δ-C14−)-lactone is demonstrated. By means of optically pure references, the order of elution S(I), R(II) was determined for the important flavour compoundsδ-octa-,δ-deca-, andδ-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 C8-, C10- and C12-δ-lactones by HRGC and multidimensional gas chromatography. Characteristic and product-specific ratios ofδ-lactone enantiomers are detected. The pattern of enantiomeric composition ofδ-octa-,δ-deca-,δ-dodecalactone in coconuts differs completely from that found in the dairy products.Zusammenfassung5-Alkyl-substituierteδ-Lactone finden sich als aromarelevante Substanzen in tierischen Fetten, aber auch in einigen Früchten. Vor kurzem gelang die erste direkte gaschromatographische Stereodifferenzierung einigerδ-Lactone an der chiralen Phase Oktakis(3-O-butyryl-2,6-di-O-pentyl)-γ-cyclodextrin [4]. Es wird nun die Enantiomerentrennung derδ-Lactone bis zu den langkettigen Verbindungenδ-Trideca-(δ-C13-)- undδ-Tetradeca-(δ-C14-)-lacton aufgezeigt. Über optisch reine Referenzsubstanzen konnte die Elutionsfolge S(I), R(II) der drei wichtigsten aromarelevanten Vertreter dieserδ-Lactonklasse bestimmt werden. Die Enantiomerenverteilung der C8-, C10-, C12-δ-Lactone im Wasserdampfdestillat verschiedener Milchprodukte (Milch, Sahne, Butter), in Margarine sowie im Kokosnußfleisch wurde exemplarisch mit Hilfe der HRGC, auch unter Einsatz der multidimensionalen Gaschromatographie (MDGC), untersucht. Es zeigten sich charakteristische, substratspezifische Enantiomerenverteilungen. Die Verteilungsmuster der untersuchten Spiegelbildisomeren aus Kokosnüssen unterschieden sich wesentlich von denen der Milchprodukte.

Enantiomer distribution of ethyl lactate : a new criterion for quality assurance of wine

Enantioselective gas chromatography using heptakis (6-0-tert.-butyldimethylsilyl-2,3-di-0-methyl)-β-cyclodextrin as the chiral stationary phase was used in chirality evaluation of ethyl lactate in wines, which is helpful in the quality assurance of wine. (S)-methyl lactate is recommended as an internal standard.