Biomedical subjects

Markus Godejohann

Publications and source records attributed to Markus Godejohann.

10 recordsLinked to original sources

PubMed2006

Hydrophilic interaction chromatography coupled to nuclear magnetic resonance spectroscopy and mass spectroscopy--a new approach for the separation and identification of extremely polar analytes in bodyfluids.

A method for the unambiguous identification of highly polar molecules based on the separation on a silica gel column run in hydrophilic interaction chromatography (HILIC) mode followed by mass spectroscopic (MS) analysis and subsequent measurement by nuclear magnetic resonance (NMR) spectroscopy is described. Polar neutral, acidic and basic compounds of small molecular size usually not retained on reversed phase stationary phases can be separated and unequivocally identified by means of MS and NMR spectroscopy. The method is applied to exemplify the identification of the endogenous metabolite trigonelline and the polar antibiotic amoxicilline in human urine.

Alkaloids↗

PubMed2006

Reaction product analysis by high-performance liquid chromatography-solid-phase extraction-nuclear magnetic resonance Application to the absolute configuration determination of naturally occurring polyyne alcohols.

The absolute configuration of secondary hydroxy functions of seven natural occurring polyyne derivatives has been elucidated by the application of Mosher method of diastereomeric methoxy-2-trifluoromethyl-phenylacetyl (MTPA) ester formation. High-performance liquid chromatography with diode array detection (HPLC-DAD) of the reaction mixture using a water/acetonitrile gradient allowed monitoring the reaction progress. Coupling of high-performance liquid chromatography to solid-phase extraction combined with nuclear magnetic resonance (HPLC-SPE-NMR) was utilized to generate highly reproducible (1)H and (19)F NMR data needed as input for the absolute configuration determination based on the analysis of relative shift differences. Chromatographic peaks of reaction substrates and reaction products bearing less 10mug analyte were trapped on SPE cartridges with the aid of water as makeup solvent. Deuterated chloroform was used to elute and transfer the peak content from the SPE to the 60mul flow cell of a 500MHz NMR spectrometer. For each analyte (1)H NMR spectra were obtained within 15min. Additionally (19)F NMR spectra were recorded for selected analytes in the same timeframe. Based on the obtained NMR data, the absolute configuration of all polyynes under investigation was successfully designated.

Alkaloids↗

PubMed2005

Studies of complex reactions using modem hyphenated methods: alpha-pinene ozonolysis as a model reaction.

Modern analytical equipment, in this case the combinations of gas chromatography (GC) with mass spectrometry (MS) and infrared spectroscopy (IR) and liquid chromatography (LC) with mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy and infrared spectroscopy, respectively, have been used to monitor complex reactions that do not only form one or two but a larger number of products. Additionally, side reactions of one primary product with a reactant form a second line of secondary products. To be able to propose formation pathways or even mechanistic interpretation of reactions like these, sophisticated analytical instrumentation is necessary to be able to observe all steps of such a reaction. In this case, the gas phase reaction of alpha-pinene with ozone has been used as a model reaction. A number of both volatile and low-volatile reaction products could be characterized and formation pathways for a reaction with ozone and OH radicals were proposed.

Bicyclic Monoterpenes↗

PubMed2005

LC-DAD-MS/SPE-NMR hyphenation. A tool for the analysis of pharmaceutically used plant extracts: identification of isobaric iridoid glycoside regioisomers from Harpagophytum procumbens.

LC-DAD-MS monitored fractionation of a Harpagophytum procumbens DC. (Pedaliaceae) root extract was combined with a hyphenated LC-DAD-MS/SPE-NMR technique, thus providing the spectral data needed for structure elucidation. This approach allowed the characterization of isobaric iridoid glycoside regioisomers present only as minor constituents. The analytes were identified as the (E/Z) pairs of 6'-O-(p-coumaroyl)harpagide (6'-PCHG) and 8-O-(p-coumaroyl)-harpagide (8-PCHG). The fact that 8-(Z)-PCHG constitutes a new natural product underlines the analytical power of this combined approach. Furthermore, derivatives 6'-(Z)- and 6'-(E)-PCHG are new constituents for H. procumbens.

Glycosides↗

PubMed2004

Characterization of a paracetamol metabolite using on-line LC-SPE-NMR-MS and a cryogenic NMR probe.

In this study, the hyphenation of LC-SPE-NMR-MS at 500 MHz was applied to the structural elucidation of a low concentrated paracetamol metabolite present in human urine. Single or multiple peak trapping of the mass detected metabolite on SPE cartridges was employed to increase the sensitivity and quality NMR measurement over the conventional LC-NMR method. After the elution of the metabolite from the SPE cartridge to the NMR flow probe using deuterated acetonitrile for initial NMR investigation, the fraction was revovered by flushing the sample out of the NMR probe head with nitrogen gas. On the recovered fraction, high resolution FT-ICR-MS measurements were conducted, giving exact mass information about the unknown metabolite. In addition, a cryogenic NMR micro probe head was used to enhance the sensitivity of the NMR measurement by a factor of 5 in order to run 2D experiments for structural elucidation of the unknown metabolite. The combination of both MS and NMR results, led unequivocally to the elucidation of the structure as the ether glucuronide of 3-methoxyparacetamol.

Acetaminophen↗

PubMed2004

Testosterone 1 beta-hydroxylation by human cytochrome P450 3A4.

Human cytochrome P450 3A4 forms a series of minor testosterone hydroxylation products in addition to 6 beta-hydroxytestosterone, the major product. One of these, formed at the next highest rate after the 6 beta- and 2 beta-hydroxy products, was identified as 1 beta-hydroxytestosterone. This product was characterized from a mixture of testosterone oxidation products using an HPLC-solid phase extraction-cryoprobe NMR/time-of-flight mass spectrometry system, with an estimated total of approximately 6 microg of this product. Mass spectrometry established the formula as C(19)H(29)O(3) (MH(+) 305.2080). The 1-position of the added hydroxyl group was established by correlated spectroscopy and heteronuclear spin quantum correlation experiments, and the beta-stereochemistry of the added hydroxyl group was assigned with a nuclear Overhauser correlated spectroscopy experiment (1 alpha-H). Of several human P450s examined, only P450 3A4 formed this product. The product was also formed in human liver microsomes.

Animals↗

PubMed2003

LC-UV-solid-phase extraction-NMR-MS combined with a cryogenic flow probe and its application to the identification of compounds present in Greek oregano.

Structure elucidation of natural products usually relies on a combination of NMR spectroscopy with mass spectrometry whereby NMR trails MS in terms of the minimum sample amount required. In the present study, the usefulness of on-line solid-phase extraction (SPE) in LC-NMR for peak storage after the LC separation prior to NMR analysis is demonstrated. The SPE unit allows the use of normal protonated solvents for the LC separation and fully deuterated solvents for flushing the trapped compounds to the NMR probe. Thus, solvent suppression is no longer necessary. Multiple trapping of the same analyte from repeated LC injections was utilized to solve the problem of low concentration and to obtain 2D heteronuclear NMR spectra. In addition, a combination of the SPE unit with a recently developed cryoflow NMR probe and an MS was evaluated. This on-line LC-UV-SPE-NMR-MS system was used for the automated analysis of a Greek oregano extract. Combining the data provided by the UV, MS, and NMR spectra, the flavonoids taxifolin, aromadendrin, eriodictyol, naringenin, and apigenin, the phenolic acid rosmarinic acid, and the monoterpene carvacrol were identified. This automated technique is very useful for natural product analysis, and the large sensitivity improvement leads to significantly reduced NMR acquisition times.

Acetone↗

PubMed2003

Application of NMR spectroscopy and LC-NMR/MS to the identification of carbohydrates in beer.

The application of LC-NMR/MS for the direct identification of carbohydrates in beer has been studied. Carbohydrates are major beer components, and their structural characterization by NMR alone is seriously hindered by strong spectroscopic overlap. Direct analysis of beer by LC-NMR/MS enables the rapid (1-2 h) identification of dextrins with degree of polymerization (DP) of up to nine monomers, with degassing being the only sample treatment required. Although the presence of alpha(1-->6) branching points is easily indicated by NMR for each subfraction separated by LC, difficulties arise for the unambiguous assignment of linear or branched forms of high DP dextrins. The two beer samples investigated in this work were found to have significantly different oligosaccharide compositions, reflecting the different production conditions employed. The use of hyphenated NMR for the rapid characterization of the carbohydrate composition of beers may be the basis of a useful tool for the quality control of beer.

Beer↗

PubMed2002

Molecular structures and associations of humic substances in the terrestrial environment.

Here we show, for the first time, evidence of the primary molecular structures in humic substances (HS), the most abundant naturally occurring organic molecules on Earth, and their associations as mixtures in terrestrial systems. Multi-dimensional nuclear magnetic resonance (NMR) experiments show us that the major molecular structural components in the mixtures operationally defined as HS are aliphatic acids, ethers, esters and alcohols; aromatic lignin derived fragments; polysaccharides and polypeptides. By means of diffusion ordered spectroscopy, distinct diffusion coefficients consistent with relatively low molecular weight molecules were observed for all the components in the mixtures, and saccharides were the largest single class of component present. Liquid chromatography NMR confirmed that HS components can be easily separated and nuclear Overhauser effect (NOE) enhancements support the finding that the components are of relatively low molecular weight <approximately 2,000 Da. The widely recognized properties of HS, i.e., characteristics indicative of crosslinked, macromolecular networks, can now be explained as aggregation of mixtures, most likely instigated by complexation with metal cations.

Animals↗

PubMed2001

An Analytical Approach for a Comprehensive Study of Organic Aerosols The financial support by the Bundesministerium für Bildung und Forschung and the Senatsverwaltung für Wissenschaft, Forschung und Kultur des Landes Berlin (ISAS Berlin), and the Ministerium für Schule, Wissenschaft und Forschung NRW (ISAS Dortmund) is gratefully acknowledged. The authors want to thank U. Marggraff and W. Nigge (Dortmund) for assistence during MS measurements and Dr. R. Köppe (Univ. Karlsruhe) and Dr. H. Sievers (GSG Karlsruhe) for assistance in FT-ICR-MS measurements.

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Journal Article↗