Complete H-1 and C-13 assignments of fluorinated analogs of dehydroepiandrosterone
ABSTRACT The complete assignments of all H-1 and C-13 chemical shifts were made for the fluorinated dehydroepiandrosterone (DHEA) analog fluasterone, 2, and two potential in vivo metabolites 3 and 4. The assignments were made using a combination of one- and two-dimensional NMR techniques (H-1, C-13, gDQCOSY, gHSQC, gHMBC). Once the proton chemical shifts were assigned, the stereochemistry of the two hydroxylated analogs was determined using 2D ROESY experiments. Copyright (c) 2006 John Wiley & Sons, Ltd.
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ABSTRACT: Dietary supplements and medicines are widely marketed over the Internet. Such products may be counterfeited and lack some or all of the labelled ingredients, or, in the case of lifestyle supplements, illegally contain pharmacologically active substances, such as anorectic or androgenic compounds. The market control - especially in the case of customs seizures - is complex, as reference substances necessary for identification and calibration in traditional high performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC-MS) analysis are often unavailable, or extremely expensive. In this study, we introduce a 400 MHz (1) H NMR methodology, which allows identification and quantitative estimation even without such pure compound standards. The identification can be based on literature spectra, or if these data are unavailable, by applying computational NMR spectra prediction. For standardless NMR determination, simple peak-area comparison of the target compound with the TSP reference was used. The applicability was demonstrated for a wide range of compounds, such as mesterolone, oxymetholone, sibutramine, monacolin K, vinpocetine, evodiamine, caffeine, kavain, and dehydroepiandrosterone. The average relative standard deviations were 5.0% for peak area comparison, and 3.3% for external calibration with standard substance. The method uncertainty is therefore higher in standardless determination, but acceptable for the purpose of proving the presence or absence of pharmacologically active substances. The limit of detection of 0.5-2 mg/kg is sufficient for the purpose. NMR is ideally suited to controlling dietary supplements or illegal medicines as it provides qualitative and at least semi-quantitative information more rapidly (measurement time 20 min) than with any other currently available spectroscopic or chromatographic method. Copyright © 2012 John Wiley & Sons, Ltd.Drug Testing and Analysis 05/2013; 5:400-411. DOI:10.1002/dta.1367 · 2.82 Impact Factor
- Cancer Epidemiology Biomarkers & Prevention 03/2009; 18(3):698-700. DOI:10.1158/1055-9965.EPI-08-1007 · 4.32 Impact Factor
- Natural Product Reports 06/2010; 27(6):887-99. DOI:10.1039/c001262a · 10.72 Impact Factor