Preferential solvation of 5,7-dihydroxyflavone (chrysin) in aqueous co-solvent mixtures of methanol and ethanol

The inverse Kirkwood-Buff integrals were used to calculate the preferential solvation parameters of the natural polyphenolic compound chrysin in binary mixtures of ethanol (1) + water (2) and methanol (1) + water (2) as a function of their thermodynamic properties. At temperatures between 298.15 K and 318.15 K, chrysin is extremely sensitive to specific solvation effects; therefore, the negative values of $\delta x_{1,3}$ were found in the water-rich range of 0 < x₁ < 0.30 for methanol (1) + water (2) and 0 < x₁ < 0.25 for ethanol (1) + water (2) which suggested that water (2) preferentially dissolves chrysin (3). In co-solvent-rich regions, the values of $\delta x_{1,3}$ were positive, and the co-solvents preferentially dissolve chrysin (3). The solvation of drugs in water-rich mixtures is likely to be facilitated by hydrophobic hydration around aromatic rings or groups.