Solubility and molecular interactions of ferulic acid in various (isopropanol + water) mixtures

Objective The solubility of an herbal compound ferulic acid (FA) in various (isopropanol (IPA) + water) mixtures was measured and correlated at temperatures ‘T = 298.2 K to 318.2 K’ and pressure ‘p = 0.1 MPa’. Methods The experimental solubilities of FA in mole fraction were determined using a static equilibrium method and correlated with ‘Apelblat, Van't Hoff, Yalkowsky and Jouyban–Acree models’. Key findings The maximum mole fraction solubilities of FA were obtained in neat IPA (2.58 × 10−2 at T = 318.2 K) followed by minimum in neat water (4.87 × 10−5 at T = 298.2 K). The activity coefficients of FA in various (IPA + water) mixtures were determined to evaluate the molecular interactions between FA and co solvent mixtures. Strong molecular interactions were seen between FA and neat IPA in comparison with FA and neat water. ‘Apparent thermodynamic analysis’ indicated an ‘endothermic and entropy‐driven dissolution’ of FA in all (IPA + water) mixtures evaluated. Conclusions Isopropanol was investigated as a good cosolvent in the solubility enhancement of FA in water; therefore, it could be used as solubilizer in solubility enhancement and formulation development of FA.