Evodiamine in several binary aqueous co-solvents: Solubility measurement and modeling, Hansen solubility parameter, preferential solvation and apparent dissolution and transfer properties

Abstract

Equilibrium solubilities of evodiamine were determined in four aqueous mixtures of methanol, isopropanol, acetone and ethanol over their full mass fraction range via the shake-flask approach covering from 283.15 to 323.15 K. The solubility profiles showed maxima in the neat cosolvents. The temperature and the mixture composition dependence of evodiamine solubility in mole fraction scale was well described by using five well-known models involving NRTL, Jouyban-Acree, van't Hoff-Jouyban-Acree, UNIQUAC and Wilson. The means of the relative deviations were recorded as 5.40%, 0.98% and 0.48% for the Wilson, UNIQUAC and NRTL models, respectively. The Jouyban-Acree and van't Hoff-Jouyban-Acree models resulted in the calculated relative average and root-mean-square deviations lower than 6.83% and 9.19 × 10−6, respectively. Hansen solubility parameter was utilized to disclose the solubility behavior of evodiamine. We also employed the linear solvation energy relationships to detect which intermolecular interactions were mainly responsible for the observed solvent effect upon solubility behavior. This analysis revealed the highlighted role of cavity term and dipolarity-polarizability of solvent in solubility variation of evodiamine. Solubility data was further examined by using the inverse Kirkwood-Buff integrals method in order to analysis the preferential solvation of evodiamine in the mixtures. Results showed the selective solvation of evodiamine by organic solvent in intermediate and organic solvent-rich compositions, and by water in water-rich compositions. The thermodynamic quantities including the apparent molar dissolution enthalpy, molar dissolution entropy and molar Gibbs energy, and the relative contribution of dissolution enthalpy and dissolution entropy to the dissolution Gibbs energy change for dissolution of evodiamine were calculated in each binary mixture. Moreover, the transfer properties were derived and discussed.