ABSTRACT
The syntheses of stable isotope labelled internal standards of important CYP-isoform selective probes, like testosterone 1, diclofenac 3, midazolam 5, and dextromethorphan 7, as well as their corresponding hydroxylated metabolites 6ß-hydroxytestosterone 2, 4'-hydroxydiclofenac 4, 1'-hydroxymidazolam 6 and dextrorphan 8 are reported. Microwave-enhanced H/D-exchange reactions applying either acid, base, or homogeneous and heterogeneous transition metal catalysis, or combinations thereof proved to be highly efficient for direct deuterium labelling of the above mentioned probes. Compared to conventional stepwise synthetic approaches, the combination of H/D exchange and biotransformation provides the potential for considerable time- and cost savings, in particular for the synthesis of the stable isotope labelled internal standards of 4'-hydroxydiclofenac 4 and 1'-hydroxymidazolam 6.
Subject(s)
Diclofenac/analogs & derivatives , Isotope Labeling/methods , Midazolam/analogs & derivatives , Pharmaceutical Preparations/chemistry , Cytochrome P-450 Enzyme System/metabolism , Deuterium Exchange Measurement , Diclofenac/chemical synthesis , Diclofenac/chemistry , Diclofenac/metabolism , Microwaves , Midazolam/chemical synthesis , Midazolam/chemistry , Midazolam/metabolism , Molecular Structure , Pharmaceutical Preparations/metabolism , Reference StandardsABSTRACT
A combination of matrix solid-phase dispersion extraction (MSPD) and LC-NMR-MS hyphenation is proposed as a rapid screening method of natural products for unknown compounds. In this report, this new analytical approach is applied for the first time. MSPD represents a significant simplification compared to classical extraction procedures and is thus an excellent complement to the fast and powerful LC-NMR-MS: MSPD yields extracts suitable for LC-NMR-MS in one simple preparation step, while LC-NMR-MS yields a wealth of information in one single chromatographic run. The suitability of this technique to characterise glycosidic compounds in the molecular mass range of 1200 to 1400 a.m.u. is demonstrated. The information on the number of exchangeable protons provided by an additional back-exchange experiment proved to be particularly valuable for structural elucidation. The possibility of semi-quantitative LC-NMR measurements through methyl signals H(3)-18 and 19 of the steroidal skeleton is demonstrated and is ensuingly used to provide relative quantitative data of the steroid oligosaccharide fraction.
Subject(s)
Biological Products/analysis , Chromatography, Liquid/methods , Mass Spectrometry/methods , Nuclear Magnetic Resonance, Biomolecular/methods , Saponins/analysis , Starfish/chemistry , Animals , Biological Products/isolation & purification , Saponins/isolation & purificationABSTRACT
Pulegone, menthone, and isomenthone isotopomers are synthesized as regioselectively deuterated d(5)- and d(8)-stereoisomers. Deuterium-labeled menthone and isomenthone enantiomers are analyzed using enantioselective multidimensional gas chromatography/mass spectrometry. The deuterated stereoisomers of menthone and isomenthone are separated from the unlabeled menthone and isomenthone on a glass capillary column, coated with 50% octakis(2, 3-di-O-butyryl-6-O-tert- butyldimethylsilyl)-gamma-cyclodextrin in OV 1701vi as the chiral stationary phase. These deuterium-labeled monoterpene ketones are proved to be highly valuable substrates in biosynthetic studies of terpenoid compounds.
Subject(s)
Ketones/metabolism , Lamiaceae/metabolism , Terpenes/metabolism , Deuterium , Gas Chromatography-Mass Spectrometry , Isotope Labeling/methods , Ketones/chemistry , Magnoliopsida/metabolism , Terpenes/chemistryABSTRACT
Mentha x piperita shoot tips and first leaf pairs were fed with aqueous solutions of different deuterium-labeled pulegone and various enantiomeric distributions. The essential oil was extracted by solid-phase microextraction and analyzed using enantioselective multidimensional gas chromatography/mass spectrometry. The genuine p-menthan-3-ones (-)-menthone and (+)-isomenthone as well as their labeled analogues were analyzed simultaneously. Both enantiomers of labeled pulegone were converted into the corresponding labeled p-menthan-3-ones by Mentha x piperita, indicating an unspecific reduction process. The generation of 4S- and 4R-configured p-menthan-3-ones differed in their stereoselectivities. Labeled (S)-pulegone was reduced by Mentha x piperita more rapidly rather than (R)-pulegone. From a comparison of labeled pulegone enantiomers the bioconversion preferrably led to 4S-configured diastereomers.
