Measurement and correlation of solubility of bioactive compound silymarin in five different green solvents at 298.15 K to 333.15 K

The objective of this study was to measure and correlate the solubility of poorly water-soluble bioactive compound silymarin in five different green solvents namely water, ethanol, isopropyl alcohol (IPA), polyethylene glycol-400 (PEG-400) and β-cyclodextrin (β-CD) solution (20 mM) from (298.15 to 333.15) K at atmospheric pressure of 0.1 MPa using the shake flask method. The experimental solubilities of silymarin were regressed by Apelblat equation and root mean square deviations (RMSDs) between calculated and experimental solubility were determined. The RMSD values were observed in the range of 0.022-2.374. However, the correlation coefficients were observed in the range of 0.997-0.999 in all green solvents investigated. The solubility of silymarin was found to be increased with temperature in all green solvents investigated. The mole fraction solubility of silymarin was found to be highest in PEG-400 (0.243 at 298.15 K) as compared to β-CD (2.10 × 10^{- 2} at 298.15 K), ethanol (1.67 × 10^{- 2} at 298.15 K), IPA (4.484 × 10^{- 3} at 298.15 K) and water (1.46 × 10^{- 5} at 298.15 K). Based on these results, silymarin was considered as practically insoluble in water, soluble in ethanol, IPA & β-CD solution and freely soluble in PEG-400.