Rutaecarpine dissolved in binary aqueous solutions of methanol, ethanol, isopropanol and acetone: Solubility determination, solute-solvent and solvent-solvent interactions and preferential solvation study

Abstract

The main objective of this work was to report the mole fraction solubility of rutaecarpine in four binary solutions of methanol (1) + water (2), isopropanol (1) + water (2), acetone (1) + water (2) and ethanol (1) + water (2) acquired through the saturation shake-flask technique. All experiments were conducted at temperatures from 283.15 K to 323.15 K. The maximum solubility was observed in the pure solvent of methanol/ethanol/isopropanol/acetone for each solution. The achieved rutaecarpine solubility in mole fraction was mathematically described by two common co-solvency models, namely Jouyban-Acree model and van’t Hoff-Jouyban-Acree model. The calculated relative average deviations were no more than 6.78%; and root-mean-square deviations, no more than 23.69 × 10−6. The linear solvation energy relationships suggested by Kamlet and Taft was used to examine the effect of solvent descriptors on the behaviour of rutaecarpine solubility. The Hildebrand solubility parameter and dipolarity-polarizability were predominant contributors to solvent effect for the four mixtures studied. The local mole fractions of methanol (acetone, isopropanol or ethanol) and water nearby the solute rutaecarpine were quantitatively analyzed through an Inverse Kirkwood–Buff integrals method. For these mixtures within intermediate and methanol/ethanol/isopropanol/acetone-rich compositions, rutaecarpine was preferentially solvated by the methanol/ethanol/isopropanol/acetone; while within water-rich compositions, by the water.