The malate-D2 1 H polarization level was estimated to be 20% in the OPE-s90 experiment. This was determined by summing the integrals of the 2.35 ppm peak during the hyperpolarized H signal decay and comparison with the thermal equilibrium signal integral after the hyperpolarization had fully decayed. We were unable to determine the 1 H polarization level in the OPE-45 experiment because the proton signal was not visible in the thermal equilibrium spectrum, but we were able to set a lower bound of 10% assuming a signal-to-noise ratio (SNR) of 1 in the thermal equilibrium spectrum.