Parahydrogen Hyperpolarization Allows Direct NMR Detection of α‐Amino Acids in Complex (Bio)mixtures

The scope of non‐hydrogenative parahydrogen hyperpolarization (nhPHIP) techniques has been expanding over the last years, with the continuous addition of important classes of substrates. For example, pyruvate can now be hyperpolarized using the Signal Amplification By Reversible Exchange (SABRE) technique, offering a fast, efficient and low‐cost PHIP alternative to Dynamic Nuclear Polarization for metabolic imaging studies. Still, important biomolecules such as amino acids have so far resisted PHIP, unless properly functionalized. Here, we report on an approach to nhPHIP for unmodified α‐amino acids that allows their detection and quantification in complex mixtures at sub‐micromolar concentrations. This method was tested on human urine, in which natural α‐amino acids could be measured after dilution with methanol without any additional sample treatment. Non‐hydrogenative parahydrogen hyperpolarization allows the detection and quantification of α‐amino acids down to sub‐micromolar concentrations. This method can also be applied to aqueous mixtures after dilution with methanol without any additional sample treatment. This direct approach was tested on human urine, allowing a well‐resolved detection of amino acids despite the complexity of the mixture.