Development of a novel functionality for a highly efficient imidazole-based ionic liquid non-aqueous solvent system for the complete extraction of target alkaloids from Phellodendron amurense Rupr. under ultrasound-assisted conditions

Abstract

Solvent application in industrial processes is inevitable due to its required role in dissolving solutes, promoting mass and heat transfer, and facilitating separation and purification processes. Notably, woody plants have a high degree of fibrosis and lignification with a mass transfer barrier effect from their multi-scale structure and complex component effects, which makes it difficult for solvents to seep into these plant cells. An ultrasound-assisted complete extraction in ionic liquid non-aqueous solvent system (UACE-ILNAS) method was successfully designed and applied to achieve excellent extraction of five alkaloid components (berberine, palmatine, jatrorrhizine, magnoflorine and phellodendrine) from the bark and leaves of Phellodendron amurense Rupr. From single-factor design and response surface methodology (RSM), the significant factors affecting the average yield of the alkaloids, the ionic liquid concentration, liquid-solid ratio and ultrasonic irradiation temperature, were optimized. Under the optimal conditions, the average yields of the alkaloids from the bark and leaves of P. amurense were 4.22 ± 0.20 and 2.47 ± 0.12 mg/g, respectively, which were highly consistent with the response surface optimization and kinetics analysis results. The non-aqueous aprotic solvent dimethyl sulfoxide (DMSO) was innovatively used as a co-solvent for the ionic liquid [C4mim][OAc]. The DMSO plays a positive role in promoting penetration, helping cell wall dissolve, reducing viscosity, etc. The proposed method overcomes the poor water solubility of isoquinoline alkaloids and the negative effects from the high viscosity of ionic liquids to effectively guarantee the alkaloid quality and yield. In addition, ultrasound plays a reinforcing role in achieving full extraction. Therefore, the developed method shows good application prospects for the separation of low-polarity constituents, especially those present in woody plants.