Effective extraction methods based on hydrophobic deep eutectic solvent coupled with functional molecularly imprinted polymers: Application on quercetagetin extraction from natural medicine and blood

Quercetagetin is one of the main active flavonoids in a well-known herbal medicine of Tagetes erecta Linn (T. erecta) flower. Selective enrichment method of quercetagetin from T. erecta flower and blood analysis method of it is lacking and need to be developed. In present study, quercetagetin based molecularly imprinted polymers (MIPs) and restricted access molecularly imprinted polymers (RAMIPs) were synthesized to separately enrich quercetagetin from deep eutectic solvent (DES) extract of T. erecta flower and plasma for the first time. Firstly, MIPs were synthesized by using quercetagetin, 2-vinylpyridine (2-VP), acetonitrile, ethylene glycol dimethylacrylate (EGDMA) and azobisisobutyronitrile (AIBN) as template, functional monomer, porogen, cross-linker and initiator, respectively. Further, RAMIPs were fabricated by introducing BSA on the surface of MIPs. The MIPs and RAMIPs were characterised using scanning electron microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analyses, and the results demonstrated the successful preparation of them. The selective adsorption properties of two kinds of polymers were further analyzed using static, dynamic and selectivity adsorption experiments. The results indicated that MIPs and RAMIPs presented good adsorption capacities (27.2 mg·g−1 and 23.1 mg·g−1) and selectivity (Imprinting factor, IF = 2.57 and 2.09 for MIPs and RAMIPs, respectively) for quercetagetin. Moreover, macromolecular exclusion experiment results revealed that almost all selected protein can be completely exclused by RAMIPs, revealing the outstanding macromolecular exclusion properties of RAMIPs. In addition, in order to environmental protection and more effective extraction of quercetagetin from T. erecta flower, organic solvent was substituted by DES. To obtain the highest extraction efficieny, the extraction parameters, including the types of DESs, solid-to-liquid ratio, extraction temperature and time were systematically optimized. By using DES-9 (L-menthol- pyruvic acid with the molar rito of 1:1) as extraction solvent, quercetagetin could be effectively extracted under the conditions of solid to liquid ratio of 5:1, extraction temperature of 30 °C and extraction time of 50 min. Following, coupled with HPLC-DAD analysis, MIPs were successfully applied as selective adsorbents for quercetagetin extraction from DES extract of T. erecta flower. Besides, in comparison with the traditional precipitation method, the absorption of quercetagetin can be more effectively elucidated by using RAMIPs.