Efficient Extraction and Mechanism Analysis of Different Polarity Phytochemicals from Rosa roxburghii by a Green CO2-Responsive Switchable Solvent Combined with Ultrasound

In this study, a green CO2-responsive switchable hydrophilic solvent (SHS) was screened in the strategy of extracting and enriching active components with different polarities from a plant matrix. The mechanism of solvent switching was confirmed by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. Furthermore, the function of SHS polarity switching was proven by Kamlet–Taft parameters, and the polarity parameter π* of the solvent increased from 0.34 to 1.01 after introducing CO2. The solvent system was used to extract the active ingredients from Rosa roxburghii; a series of single factor experiments were conducted using the Box-Behnken design in order to optimize the process. In addition, the phenomenon of the SHS/water two-phase system being heated by ultrasound to produce an O/W micellar system was observed, which provided solvent solubilization. Moreover, after 5 cycles, the solvent still ensured a high extraction capacity of the target components. In addition, density functional theory (DFT) and molecular dynamics theory revealed that van der Waals forces and hydrogen bonding made the SHS more biocompatible with the target compounds and that van der Waals forces played a significant impact. In conclusion, the current process offered an ecologically acceptable, promising, and long-term alternative approach for simultaneously extracting and enriching hydrophilic and hydrophobic phytochemicals from plant materials.