Solubility data, Hansen solubility parameters and thermodynamic behavior of pterostilbene in some pure solvents and different (PEG-400 + water) cosolvent compositions

Abstract

The solubility and other important physicochemical properties of naturally derived bioactives such as pterostilbene (PT) are rarely reported. With this background, the solubility, Hansen solubility parameters and thermodynamic behavior of PT in five pure solvents and different polyethylene glycol-400 (PEG-400) + water cosolvent compositions at “T = 298.2 K to 318.2 K" and “p = 0.1 MPa” were studied and reported in this research. The obtained experimental solubility data of PT was regressed well with six theoretical models including van't Hoff, Apelblat, Buchowski-Ksiazaczak λh, Yalkowsly-Roseman, Jouyban-Acree and van't Hoff-Jouyban-Acree models. The solubilities of PT (expressed in mole fraction) were found to be highest in pure PEG-400 (3.73 × 10−1) followed by PG (2.90 × 10−1), THP (2.53 × 10−1), ethanol (1.36 × 10−1) and water (2.95 × 10−5) at “T = 318.2 K”. The same trends of solubility were also recorded at other temperatures. PT was found to be freely soluble in all solvents studied except water. Thermodynamic evaluation indicated an endothermic and entropy-driven dissolution of PT in PEG-400, PG, THP, ethanol, water and all “PEG-400 + water” cosolvent compositions. Enthalpy-entropy compensation analysis suggested enthalpy-driven mechanism as the main mechanism for PT solvation. The results of activity coefficients indicated higher molecular interactions in PT-PEG-400 compared to other PT-solvents combinations. Based on all physicochemical data, PEG-400 was found to be the best solvent for the solubilization of PT, although ethanol, PG and THP were also suitable for the solubilization of PT.