Insight into the mechanism of efficient extraction of tea saponins from Camellia oleifera shells using deep eutectic solvents

Abstract

Camellia oleifera (C. oleifera) shells, a major by-product of the camellia oil industry, are rich in tea saponins. The efficient extraction and characterization of tea saponins from C. oleifera shells using deep eutectic solvents (DESs) were investigated, with the extraction mechanism further explored through scanning electron microscopy (SEM) and molecular dynamics simulations. A total of 24 different types of DESs were prepared, with the optimal DES identified as a combination of L-proline and acetamide (the molar ratio of 1:4). Response surface methodology (RSM) optimization revealed that the maximum yield of tea saponins extraction reached 22.46 %. 18 kinds of tea saponin monomers were identified by ultrahigh-performance liquid chromatography coupled with quadrupole-orbitrap high-resolution mass spectrometry (UPLC-Q-Orbitrap HRMS). SEM analysis showed that DESs effectively disrupted the surface structure of C. oleifera shell. Furthermore, molecular dynamics simulations demonstrated the high extraction efficiency of DESs was due to their larger solvent accessible surface area (SASA), increased number of hydrogen bonds, extended hydrogen bond lifetime, and lower intermolecular interaction energy between DESs and tea saponins. These findings provide new insights into the extraction mechanism and contribute to the optimization of DES-based extraction techniques for bioactive compounds from natural plant sources.