Simultaneous Extraction and Separation of Different Polarity Phytochemicals from in Pigeon Pea Leaves with Biphasic Temperature-Switchable Deep Eutectic Solvent System

Pigeon pea is one of the world’s most valuable food crops, an important cash crop, and the only woody legume crop with both medicinal and healthy functions. In this paper, a biphasic temperature-switchable deep eutectic solvent (biphasic-TSDES) system, consisting of a hydrophilic deep eutectic solvent (choline chloride/levulinic acid) and hydrophobic deep eutectic solvent (octanoic acid /lauric acid), was designed and prepared to extract hydrophilic and hydrophobic active components from pigeon pea leaves. Combining the ultrasound-assisted extraction technique with total extraction and partitioning efficiency as response values, seven primary active substances in pigeon pea leaves were extracted. Under the optimal process parameters, the extraction efficiency was much higher than that of other conventional organic solvents, and the total extraction efficiency reached 20.780 ± 0.285 mg/g. Subsequently, hydrophilic and hydrophobic compounds in the extract were recycled separately, and the recovery efficiency of cajaninstilbene acid, the most critical hydrophobic active substance in pigeon pea leaves, reached 97.17 %. Moreover, the hydrophilic target compounds were almost completely recovered. The novel green solvent system could provide references for simultaneous high-temperature homogeneous extraction and low-temperature heterogeneous separation for different polarity phytochemicals from plants.