Magnetic dual-template molecularly imprinted polymers for separation and enrichment of echinacoside and acteoside from Cistanche deserticola Y. C. Ma

Abstract

A creative dual-template molecularly imprinted polymer (Fe3O4 @MCM-41-MIPs) with good magnetic properties and specific recognition of echinacoside and acteoside was prepared by surface imprinting. Echinacoside and acteoside served as dual templates, 4-vinylpyridine (4-VP) was used as a functional monomer, the cross-linker was ethylene glycol dimethacrylate (EGDMA), and the selected initiator was azobisisobutyronitrile (AIBN). The prepared Fe3O4 @MCM-41-MIPs were applied to the selective separation and enrichment of echinacoside and acteoside from Cistanche deserticola Y. C. Ma (C. deserticola). The resulting Fe3O4 @MCM-41-MIPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), laser particle size scanning and vibration sample magnetometry (VSM). The results of the isotherm adsorption experiment showed that the maximum adsorption capacities of Fe3O4 @MCM-41-MIPs for echinacoside and acteoside were 6.02 and 1.63 mg·g-1, respectively, at 298 K. The pseudo-second-order reaction mechanism showed that the equilibrium adsorption capacities of Fe3O4 @MCM-41-MIPs for echinacoside and acteoside were 4.81 and 0.93 mg·g-1, respectively. The characterization of Fe3O4 @MCM-41-MIPs showed that the imprinted layer with dual-template molecules was wrapped on the outside of the carrier, and the obtained Fe3O4 @MCM-41-MIPs showed good saturation magnetization, desirable capacity for echinacoside and acteoside adsorption, and satisfactory reuse (echinacoside and acteoside maintained relative adsorption rates of 97.5% and 95.8% after five cycles). After separation, the purities of echinacoside and acteoside were 33.50% and 27.00%, respectively. In addition, in the selective adsorption experiment, the synthesized Fe3O4 @MCM-41-MIPs showed better selectivity for echinacoside and acteoside than their structural analogs. Therefore, this method proved to be sustainable, rapid and highly efficient for the separation and enrichment of echinacoside and acteoside.