Hydroxycinnamic acids in supercritical carbon dioxide. The dependence of cosolvent-induced solubility enhancement on the selective solvation.

• Simulation of hydroxycinnamic acids in cosolvent-modified supercritical CO 2 was performed. • Solvation free energies were calculated using the Bennett's acceptance ratio method. • Cosolvent-induced solubility enhancements have been estimated. • Cosolvent-induced effect decreases with increasing pressure. • Cosolvent-induced solubility enhancement correlates with number of solute's hydrogen bonds. Simulation of hydroxycinnamic acids (caffeic, p-coumaric, ferulic, synapic) in pure and modified by polar cosolvents (methanol, acetone) supercritical carbon dioxide has been carried out using classical molecular dynamics. Dependences of solvation free energies of the acids on the pressure and cosolvent mole fraction have been calculated using Bennett's acceptance ratio method. When a polar cosolvent is added, the solvation free energy decreases sharply, and with a subsequent increase in its concentration, it changes slightly. The cosolvent-induced effect decreases with increasing pressure. The structural parameters characterizing the selective solvation of the acids have been calculated. A correlation between the cosolvent-induced solubility enhancement and the average number of solute – cosolvent hydrogen bonds has been found. [ABSTRACT FROM AUTHOR]