pH-controlled reversible deep-eutectic solvent based enzyme system for simultaneous extraction and in-situ separation of isoflavones from Pueraria lobata

In this study, we developed an efficient and green pH-controlled reversible deep-eutectic solvents (DESs) based enzyme system for efficient extraction, transformation and in-situ separation of natural products from herbs. As a case study, seven isoflavones in the root of Pueraria lobata were selected as target compounds. A series of DESs were firstly prepared and the extraction efficiency for target compounds with or without cellulase catalysis was investigated. We found that [N4444][Cl]:ethylene glycol (1:2) with cellulase addition show the highest extraction efficiency for isoflavones. More importantly, the phase behavior of [N4444][Cl]:ethylene glycol (1:2) based cellulase system was found to be pH-controlled. When pH is 5.0, the system is a homogeneous single-phase system, which is conducive to the extraction of natural products. When pH is 6.4, the system changes from the single-phase to the heterogeneous two-phase, to realize the in-situ separation of the compounds. Therefore, by adjusting the pH of the system, the in-situ separation of isoflavones was successfully realized with high recovery yields. The pH-controlled DESs based enzyme-assisted extraction system overcomes the incompatibility between enzyme catalysis and conventional organic solvent in extraction, which could efficiently extract seven isoflavones from Pueraria lobata root.