A greener and sustainable route for medicinal plant analysis: Recycle utilization of hydrophobic deep eutectic solvent

The green and efficient extraction of bioactive compounds from plant biomass is an extraordinary area of interest in the pharmaceutical industries. In a perspective of sustainable development, we investigate an eco-friendly route using recycle hydrophobic deep eutectic solvent-assisted water extraction (RHD-WE) to effectively and simultaneously extract five main phenolic acids (caftaric acid, chlorogenic acid, caffeic acid, cichoric acid, 3,5-di-O-caffeoylquinic acid) from medicinal plant. In the procedure, 20 mg Taraxacum mongolicum powder was mixed with 800 µL water and 200 µL camphor/p-chlorophenol-based hydrophobic deep eutectic solvent (DES) at a molar ratio of 1:3. After 10 min vortex and centrifugation, the mixture was separated into aqueous phase and DES phase. Compared with other published procedures, phenolic acids were enriched in the aqueous phase. Aqueous solution of phenolic acid could be directly used as raw materials without further purification in pharmaceutical industries. Besides, hydrophobic DES phase could easily be recovered and reused in recycling studies. This is the first study of the recyclability of hydrophobic DES. Generally speaking, the model for the extraction of phenolic acids was well established and verified. The extraction efficiency was higher than other traditional extraction methods, approximately 14 mg/g of phenolic acids were obtained in the aqueous phase. In addition, the extraction mechanism was preliminarily discussed in this research. Such novel RHD-WE method might improve the existing schemes for extraction of bioactive compounds from plant materials. This study suggested that hydrophobic DESs could be used as green and safe auxiliary extractant for pharmaceutical applications.