13C-formylation for improved nuclear magnetic resonance profiling of amino metabolites in biofluids.

An increased interest in metabolite profiling is driving the need for improved analytical techniques with greater performance for a variety of important applications. Despite their limited sensitivity, nuclear magnetic resonance (NMR) methods are attractive because of their simplicity, reproducibility, quantitative nature, and wide applicability. The use of chemoselective isotopic tags has the potential to advance the application of NMR for analyzing metabolites in complex biofluids by allowing detection of metabolites down to the low micromoalr level with high resolution and specificity. Here, we report a new (13)C-tagging method using (13)C-formic acid that delivers high sensitivity, good quantitation, and excellent resolution for (1)H-(13)C 2D NMR profiling of amino metabolites. High reproducibility (coefficient of variation (CV) = 2%) was observed for metabolites in urine with concentrations down to 10 microM. As amino compounds comprise an important class of metabolites and small molecules of biological roles, this new method therefore should be amenable to a variety of applications.