Solvation Free Energy for Selection of an Aqueous Two-Phase System: Case in Paeonol Extraction from Cortex Moutan

Aqueous two-phase system(s) (ATPS) has/have been widely employed in the extraction and separation of bioactive molecules from herbs due to its various advantages such as high efficiency and good selectivity. For selecting the type and amount of organics and salts in ATPS, onerous experimental trials are required to ensure the reliability. We intended to develop a theoretical method to select ATPS in the case of paeonol extraction from cortex moutan. The solvation free energies (E-solv) of paeonol in the top phase of 54 ATPS (ATPS-acetone, ATPS-acetone-EA, ATPS-THF, ATPS-THE-EA, ATPS-EtOH, and ATPS-EtOH-EA) were calculated with Gaussian 09, and the extraction yields with 54 ATPS were determined. By comparison of E-solv and yield, the E-solv rank was effective to select the optimal organic type and organic solvent fraction and aqueous salt concentration. With each series of 18 ATPS (ATPS-acetone plus ATPS-acetone-EA; ATPS-THF plus ATPS-THE-EA; or ATPS-EtOH plus ATPS-EtOH-EA), the paeonol yield was correlated with E-solv, suggesting that the optimal organic type and fraction and the aqueous NaH2PO4 concentration could be selected by using theoretical E-solv, or at least, the theoretical E-solv rank could offer effective guidance for experimental design, and thus, tedious and onerous experimental work for optimization in ATPS extraction can be significantly reduced.

Automated summary

This study aimed to develop a theoretical method for selecting the aqueous two-phase system (ATPS) for paeonol extraction from cortex moutan. The solvation free energies (E-solv) of paeonol were calculated in different ATPS, and their ranking was compared with the extraction yield. The results showed that E-solv ranking was effective in selecting the optimal organic type, organic solvent fraction, and aqueous salt concentration. The use of theoretical E-solv can significantly reduce the tedious experimental work for optimization in ATPS extraction.