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How does nuclear magnetic resonance spectroscopy examine metabolites?

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Diagram illustrating metabolism with two sections: anabolic reaction on the left shows energy used to build larger molecules from smaller ones, while catabolic reaction on the right shows larger molecules breaking down into smaller molecules with energy released. — Metabolomics In anabolic reactions, a cell uses energy to combine small molecules into larger molecules. In catabolic reactions, molecules are broken down, and energy is released.

In the context of metabolomics, nuclear magnetic resonance (NMR) spectroscopy serves as a rapid, reproducible technique for investigating metabolites while preserving the integrity of the biological specimen.1

The process functions by placing a sample in a strong external magnetic field, which causes certain atomic nuclei—such as hydrogen ( $^{1}$ H) or carbon-13 ( $^{13}$ C)—to behave like tiny magnets and assume specific energy states. When these nuclei are irradiated with radio-frequency waves, they absorb energy at specific frequencies, a phenomenon known as resonance.234

Because the energy required for this absorption is significantly modified by the immediate chemical environment of the nucleus, NMR provides detailed information regarding the molecular structure of the metabolites present. While NMR is highly valued for its ability to yield structural data without destroying the sample, it is characterized by limited sensitivity and typically detects only a relatively small number of metabolites in biological samples compared to other methods like mass spectrometry.4231