Hesperetin Solubility in Aqueous Co-solvent Mixtures of Methanol and Ethanol: Solute Descriptors, Solvent Effect and Preferential Solvation Analysis

Solubility data for hesperetin in pure solvents and alcohol-rich regions of aqueous mixtures of methanol and ethanol were used to derive the solute descriptors for solubility prediction of hesperetin by using the Abraham solvation parameter model. Solubility data in aqueous mixtures of methanol and ethanol were analyzed by the linear solvation energy relationships approach to provide detailed insight into the solvent effect. In this regard, energy terms for solute-solvent and solvent-solvent interactions were defined in terms of dipolarity-polarizability, hydrogen bond basicity, hydrogen bond acidity and Hildebrand solvent parameter. Results indicate that the main contribution was from solvent-solvent interactions represented by the cavity term. Preferential solvation analysis was performed with the help of inverse Kirkwood-Buff integrals approach. Local composition and preferential solvation parameter were calculated as a function of mole fraction of methanol and ethanol. Results show that hesperetin is preferentially surrounded by water in water-rich regions, whereas methanol or ethanol are preferred in other compositions. This observation was discussed in terms of the solute hydrophobic hydration and specific hydrogen bonding interactions.