Solubility Determination, Hansen Solubility Parameters and Thermodynamic Evaluation of Thymoquinone in (Isopropanol + Water) Compositions.

This article studies the solubility, Hansen solubility parameters (HSPs), and thermodynamic behavior of a naturally-derived bioactive thymoquinone (TQ) in different binary combinations of isopropanol (IPA) and water (HO). The mole fraction solubilities () of TQ in various (IPA + HO) compositions are measured at 298.2-318.2 K and 0.1 MPa. The HSPs of TQ, neat IPA, neat HO, and binary (IPA + HO) compositions free of TQ are also determined. The data of TQ are regressed by van't Hoff, Apelblat, Yalkowsky-Roseman, Buchowski-Ksiazczak , Jouyban-Acree, and Jouyban-Acree-van't Hoff models. The maximum and minimum values of TQ are recorded in neat IPA (7.63 × 10 at 318.2 K) and neat HO (8.25 × 10 at 298.2 K), respectively. The solubility of TQ is recorded as increasing with the rise in temperature and IPA mass fraction in all (IPA + HO) mixtures, including pure IPA and pure HO. The HSP of TQ is similar to that of pure IPA, suggesting the great potential of IPA in TQ solubilization. The maximum molecular solute-solvent interactions are found in TQ-IPA compared to TQ-HO. A thermodynamic study indicates an endothermic and entropy-driven dissolution of TQ in all (IPA + HO) mixtures, including pure IPA and pure HO.