Journal Highlight: Combined use of filtered and edited ¹H NMR spectroscopy to detect ¹³C-enriched compounds in complex mixtures

Combined use of filtered and edited ¹H NMR spectroscopy to detect ¹³C-enriched compounds in complex mixtures

NMR in Biomedicine, 2012, 25, 1217-1223
P. W. A. Howe, Z. Ament, K. Knowles, J. L. Griffin, J. Wright

Abstract: In conventional metabolism and pharmacokinetic studies, radioactive isotopes are used to identify and quantify the breakdown products of xenobiotics. However, the stable isotope ¹³C provides a cheaper and less hazardous alternative. Metabolites of ¹³C-enriched xenobiotics can be detected, quantified and identified by ¹³C-filtered NMR spectroscopy. However, one obstacle to using ¹³C is its 1.1% natural abundance that produces a background signal in ¹³C-filtered NMR spectra of crude biological extracts. The signal makes it difficult to distinguish between ¹³C-enriched xenobiotics resonances from endogenous metabolites unrelated to the xenobiotic. This study proposes that the ¹³C background signal can be distinguished from resonances of ¹³C-enriched xenobiotics by the absence of a ¹²C component in the xenobiotic. This is detected by combined analysis of ¹³C-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 ¹³C-enriched phenacetin in crude extracts of hepatocyte microsomes.

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