ParaHydrogen Induced Polarization of 13C carboxylate resonance in acetate and pyruvate

The advent of nuclear spins hyperpolarization techniques represents a breakthrough in the field of medical diagnoses by magnetic resonance imaging. Dynamic nuclear polarization (DNP) is the most widely used method, and hyperpolarized metabolites such as 1-13C-pyruvate are shown to report on status of tumours. Parahydrogen-induced polarization (PHIP) is a chemistry-based technique, easier to handle and much less expensive in respect to DNP, with significantly shorter polarization times. Its main limitation is the availability of unsaturated precursors for the target substrates; for instance, acetate and pyruvate cannot be obtained by direct incorporation of the parahydrogen molecule. Herein we report a method that allows us to achieve hyperpolarization in this kind of molecule by means of a tailored precursor containing a hydrogenable functionality that, after polarization transfer to the target 13C moiety, is cleaved to obtain the metabolite of interest. The reported procedure can be extended to a number of other biologically relevant substrates. Compounds such as acetate and pyruvate are useful probes for MRI, but their hyperpolarization relies on difficult and expensive dynamic nuclear polarization techniques. Here, the authors show how parahydrogen-induced polarization can be used to quickly and inexpensively hyperpolarize these compounds.