Dissolution thermodynamics and solubility of silymarin in PEG 400-water mixtures at different temperatures

Abstract

An isothermal method was used to measure the solubility of silymarin in binary polyethylene glycol 400 (PEG 400) + water co-solvent mixtures at temperatures T = 298.15–333.15 K and pressure p = 0.1 MPa. Apelblat and Yalkowsky models were used to correlate experimental solubility data. The mole fraction solubility of silymarin was found to increase with increasing the temperature and mass fraction of PEG 400 in co-solvent mixtures. The root mean square deviations were observed in the range of 0.48–5.32% and 1.50–9.65% for the Apelblat equation and Yalkowsky model, respectively. The highest and lowest mole fraction solubility of silymarin was observed in pure PEG 400 (0.243 at 298.15 K) and water (1.46 × 10⁻⁵ at 298.15 K). Finally, thermodynamic parameters were determined by Van’t Hoff and Krug analysis, which indicated an endothermic and spontaneous dissolution of silymarin in all co-solvent mixtures.

• Apelblat equation
• dissolution thermodynamics
• silymarin
• solubility
• yalkowsky model

Declaration of interest

The authors report no conflict of interest. The authors would like to extend their sincere appreciation to the Kayyali Chair for Pharmaceutical Industry at King Saud University for supporting this work (FN-2015, Research Chair, Deanship of Scientific Research).

Supplementary Material available online.

Supplemental Tables S1 and S2, Figures S1 and S2.