On the solubility of quercetin

There is a considerable disagreement over the solubility of quercetin in water. Experimental values of log Cw with Cw in mol/L range from − 2.52 to − 5.89, a difference of over three log units. We have applied a methodology based on linear free energy equations for water-solvent and gas-solvent partitions to study solubilities. These are related to partition coefficients through Ps = Cs/Cw where Cs and Cw are solubilities of a given solute in a solvent and in water. We find that known solubilities of quercetin in methanol and ethanol at 298 K and a known water-solvent partition coefficient can be accommodated in the same model if the water solubility at 298 K, as log Cw, is taken as − 3.90, that is near to the middle of the range of experimental values. Our model successfully predicts solubilities of quercetin in water–ethanol mixtures near to the ethanol rich mixtures.