title: Combined use of filtered and edited 1 H NMR spectroscopy to detect 13 C-enriched compounds in complex mixtures.
abstract: In conventional metabolism and pharmacokinetic studies, radioactive isotopes are used to identify and quantify the breakdown products of xenobiotics. However, the stable isotope (13) C provides a cheaper and less hazardous alternative. Metabolites of (13) C-enriched xenobiotics can be detected, quantified and identified by (13) C-filtered NMR spectroscopy. However, one obstacle to using (13) C is its 1.1% natural abundance that produces a background signal in (13) C-filtered NMR spectra of crude biological extracts. The signal makes it difficult to distinguish between (13) C-enriched xenobiotics resonances from endogenous metabolites unrelated to the xenobiotic. This study proposes that the (13) C background signal can be distinguished from resonances of (13) C-enriched xenobiotics by the absence of a (12) C component in the xenobiotic. This is detected by combined analysis of (13) C-filtered and -edited NMR spectra. The theory underlying the approach is described and the method is demonstrated by the detection of sub-microgram amounts of (13) C-enriched phenacetin in crude extracts of hepatocyte microsomes.
authors.affiliation: Syngenta, Jealott's Hill Research Centre, Bracknell, RG42 6EY, UK. peter.howe@syngenta.com
authors.forename: P W A
authors.initials: PW
authors.lastname: Howe
authors.forename: Z
authors.initials: Z
authors.lastname: Ament
authors.forename: K
authors.initials: K
authors.lastname: Knowles
authors.forename: J L
authors.initials: JL
authors.lastname: Griffin
authors.forename: J
authors.initials: J
authors.lastname: Wright
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D045424:Complex Mixtures / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D010615:Phenacetin / Q000737:chemistry / Q000494:pharmacology; D011522:Protons; D051381:Rats
chemical_list: D002247:Carbon Isotopes; D045424:Complex Mixtures; D011522:Protons; D010615:Phenacetin