A comprehensive analysis of low molecular weight compounds in biological samples by the hyphenated method of GC/MS in general detects a large number of peaks which can not be identified by searching of commercially available mass spectral libraries. Therefore, more information is required for a successful identification of these compounds. Some structural features like molecular weight and number of derivatization groups present in the molecule can be determined by variation of the derivatization prior to GC/MS. The use of deuterated derivatizing reagents and the newly developed N-methyl-N-ethyldimethylsilyl-trifluoracetamide for this purpose is described. The knowledge of these structural properties alone undoubtedly will not lead to the structure elucidation of novel metabolites. However, it may be helpful in identifying derivatives of known metabolites or artifacts. Thus, by use of the molecular weight as search criterion it is possible to find plausible candidates in metabolic pathway databases. It is shown that the application of this method to a hydrophilic extract of C. glutamicum lead to the identification of 31 in previous analyses unidentified peaks, in their majority representing minor derivatives of common metabolites.
Fractionation of the lipid extract from rhizomes of Iris hoogiana Dykes resulted in the isolation of one new and several known iridals. The latter were identified by comparison with authentic standards as 1 ± 5. The structure of the new natural product, hoogianal (11), was elucidated by spectroscopic analysis. Oxidative degradation yielded b-irone (10), identified by GC-and LC-MS. The (À)-(2S)-configuration of this oxidation product was determined by enantioselective GC on a chiral cyclodextrin phase and by comparison with the corresponding ketones in laevo-and dextrorotatory commercial Iris oils.Helvetica Chimica Acta ± Vol. 84 (2001) 933 1 ) Abbreviations: HPLC high performance liquid chromatography, MPLC medium pressure liquid chromatography; ESI electrospray ionization; APCI atmospheric-pressure chemical ionization; DAD diode-array detector.2 ) The C-skeleton of the iridals is numbered in analogy to squalene. For the systematic name of 11, see Exper.Part.
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