ABSTRACT
This chapter explains how untargeted metabolomics is applied to biospecimens from intervention or observational studies for biomarker discovery. The most widely used analytical technologies for metabolomics are currently based on either nuclear magnetic resonance (NMR) or mass spectrometry (MS) coupled with liquid chromatography (LC) or gas chromatography (GC). The main advantage of NMR in metabolomics lies in its quantitative nature and in its ability to detect certain unique features such as blood lipoproteins. Metabolomics is inherently suited to food biomarker discovery. The main prerequisite for effective biomarker discovery with MS-based systems is the acquisition of high-resolution mass spectra with accurate mass measurement. Regardless of the type of the MS instrument, metabolomics methods can be broadly divided between direct analysis of the sample and separation-based techniques. Hydrophilic interaction chromatography (HILIC) in particular has been found to be complementary to reversed phase in metabolomics and has enabled successful analysis of highly polar dietary metabolites such as malic acid and amino acid-derived betaines.
