Abstract
Solubility data of bioactive compound such as thymoquinone (THQ) are scarce in research community. Therefore, in present study, solubility, solubility parameters, solution thermodynamics and solute-solvent interactions (at molecular level) of THQ in eleven mono solvents including “water (H2O), propylene glycol (PG), polyethylene glycol-400 (PEG-400), methanol (MeOH), ethanol (EtOH), isopropanol (IPA), 1-butanol (1-BuOH), 2-butanol (2-BuOH), ethyl acetate (EA), dimethyl sulfoxide (DMSO) and Transcutol® (THP)” at five different temperatures i.e. “T = 298.2 K, 303.2 K, 308.2 K, 313.2 K and 318.2 K” and constant pressure “p = 0.1 MPa” were studied. The characterization of solid phases of THQ suggested no transformation of THQ into polymorphs/solvates. Measured solubility data of THQ was regressed by “van't Hoff and Apelblat models” with overall deviations of 1.00 and 0.56%, respectively. Experimental solubilities of THQ (expressed in mole fraction) were recorded highest in THP followed by 2-BuOH, 1-BuOH, IPA, PEG-400, EA, DMSO, EtOH, MeOH, PG and H2O at “T = 318.2 K”. Same tendencies were also recorded at each temperature point studied. Ideal/theoretical solubilities of THQ were estimated using its thermal parameters at five different temperatures. Ideal solubilities of THQ were recorded much higher than experimental solubilities of THQ at each temperature. With the help of ideal solubilities of THQ, activity coefficients were estimated. Based on estimated values of activity coefficients, highest interactions at molecular level were recorded in THQ-THP. “Apparent thermodynamic analysis” data showed “endothermic and entropy-driven dissolution” of THQ in each mono solvent studied.
•Solubility of thymoquinone (THQ) in different mono solvents was estimated.•The highest mole fraction solubilities of THQ were obtained in Transcutol.•Experimental solubilities of THQ were correlated well with calculated ones.•The dissolution of THQ was recorded as endothermic and entropy-driven.