Solubility Determination, Modeling, and Solvent Effect Analysis of Tanshinone I in Several Solvents at (278.15–323.15) K

The equilibrium mole fraction solubility of tanshinone I in acetone, N,N-dimethylformamide (DMF), methanol, ethanol, water, ethylene glycol (EG), n-propanol, isopropanol, and 1-butanol as well as methanol/ethanol/DMF/acetone + water was determined by the isothermal saturation method at 278.15–323.15 K under 101.2 kPa. The temperature and the composition of solvent mixtures play a decisive role in the solubility of tanshinone I. Then, four monosolvent models (Apelblat, van’t Hoff, λh, and NRTL) and three cosolvency models (Jouyban–Acree (J-A), van’t Hoff–Jouyban–Acree (V-J-A), and modified Apelblat–Jouyban–Acree (A-J-A)) were utilized to correlate the mole fraction of tanshinone I. The maximum deviation (relative average deviation (RAD) and root-mean-square deviation (RMSD)) between the experimental data and the solubility data calculated by the monosolvent models are 6.21% and 3.02 × 10–4, respectively. The maximum of RAD and RMSD for the mixture systems are 1.58% and 1.35 × 10–4, respectively. The Kamlet and Taft linear solvation energy relationship model was used to analyze the solvent effect, and the nonspecific dipolarity/polarizability interactions between the solute and solvent played a major promoting role. All in all, the experimental and computational data are able to provide basic data for the optimization and improvement of the recrystallization process of tanshinone I.