  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 on 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.
