Effect of the hydrogenation solvent in the PHIP-SAH hyperpolarization of [1-13C]pyruvate

ParaHydrogen Induced Polarization-Side Arm Hydrogenation (PHIP-SAH) is an inexpensive tool to obtain hyperpolarized pyruvate (and other metabolites) that can be applied to in vivo diagnostics, for the investigation of metabolic processes. This method is based on hydrogenation, using hydrogen enriched in the para-isomer, of unsaturated substrates, catalyzed, usually, by a homogeneous rhodium(I) complex. In this work, the effect of the solvent on the hydrogenation efficiency and the hyperpolarization level were investigated. Coordinating solvents, such as acetone and methanol, can increase significantly either the efficiency or the hyperpolarization level, but they are not compatible with the intended metabolic applications. The phase extraction of the hyperpolarized product (sodium pyruvate) in an aqueous solution was obtained carrying out the hydrogenation reaction in chloroform and toluene. The traces of the organic solvents in the water phase were removed, by means of filtration through a lipophilic resin, thus improving the biocompatibility of the aqueous solution of the hyperpolarized product.

Automated summary

ParaHydrogen Induced Polarization-Side Arm Hydrogenation (PHIP-SAH) is an inexpensive tool for obtaining hyperpolarized pyruvate for in vivo diagnostics. The solvent used in the hydrogenation process can affect efficiency and hyperpolarization level. Coordinating solvents can significantly increase efficiency or hyperpolarization level, but may not be compatible with metabolic applications. The extraction of hyperpolarized product in an aqueous solution can improve biocompatibility by removing traces of organic solvents.