title: Quercetin-imprinted chromatographic sorbents revisited: optimization of synthesis and rebinding protocols for application to natural resources.
abstract: Molecularly imprinted polymers (MIPs) based on quercetin and synthesized by either bulk, precipitation or suspension polymerization were characterized in terms of size and shape by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After a study of rebinding protocols, the optimal materials were evaluated as sorbents for solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) to confirm the presence of imprinted cavities and to assess their selectivity. Besides quercetin, other structurally related natural compounds, naringenin, daidzein and curcumin, were employed for selectivity tests of MIPs. Although rebinding protocols previously described for such MIPs are typically based on binding, washing and eluting methanol-based solutions, we show that this highly polar solvent leads to weak specific interactions (imprinting factor<1) and poor sorbent properties, most probably because of hydrogen-bonding interferences between the MIP and MeOH. Similar experiments performed in tetrahydrofuran yield to much more improved properties (imprinting factor>2.4). This calls for reviewing most of previously published data on quercetin-MIPs; in proper binding conditions, published MIPs may prove more performing than initially assessed. As expected, tested MIPs exhibited the highest selective rebinding towards quercetin template (imprinting effect, quercetin, 3.41; naringenin, 1.54; daidzein, 1.38; curcumin, 1.67); the differences in selectivity between quercetin analogues were explained by the ligand geometries and H-bonding patterns obtained from quantum-chemical calculations. The evaluation of MIPs under identical analytical conditions allowed investigating the effect of the production method on chromatographic performances. The MIPs in bead materials (for quercetin, peak width, 0.69; number of theoretical plates, 143; symmetry factor, 2.22) provided a significant improvement in chromatographic efficiency over the bulk materials (for quercetin, peak width, 1.25; number of theoretical plates, 115; symmetry factor, 2.92). Using the quercetin-beaded MIP as SPE sorbent, quercetin was selectively extracted from Allium cepa L. extract. The MIP developed in this work therefore appears highly promising for the enrichment and determination of quercetin in natural products.
authors.affiliation: Laboratory of Therapeutic Chemistry and Pharmacognosy, Faculty of Medicine and Pharmacy, University of Mons - UMONS, Place du Parc 20, 7000 Mons, Belgium(1); Laboratory of Polymeric and Composite Materials, Center of Innovation and Research in Materials and Polymers (CIRMAP), University of Mons - UMONS, Place du Parc 20, 7000 Mons, Belgium; Laboratory of Pharmaceutical Analysis, Faculty of Medicine and Pharmacy, University of Mons - UMONS, Place du Parc 20, 7000 Mons, Belgium; Research Institute for Health Sciences and Technology and Research Institute for Biosciences, Belgium. Electronic address: pierre.duez@umons.ac.be.
authors.forename: Antonelle
authors.initials: A
authors.lastname: Pardo
authors.affiliation: Laboratory of Polymeric and Composite Materials, Center of Innovation and Research in Materials and Polymers (CIRMAP), University of Mons - UMONS, Place du Parc 20, 7000 Mons, Belgium.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Mespouille
authors.affiliation: Laboratory of Pharmaceutical Analysis, Faculty of Medicine and Pharmacy, University of Mons - UMONS, Place du Parc 20, 7000 Mons, Belgium; Research Institute for Health Sciences and Technology and Research Institute for Biosciences, Belgium.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Blankert
authors.affiliation: INSERM UMR-S850, Faculté de Pharmacie, Université de Limoges, 2 rue du Docteur Marcland, 87025 Limoges Cedex, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Trouillas
authors.affiliation: Laboratory for Chemistry of Novel Materials, Center of Innovation and Research in Materials and Polymers (CIRMAP), University of Mons - UMONS, Place du Parc 20, B-7000 Mons, Belgium.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Surin
authors.affiliation: Laboratory of Polymeric and Composite Materials, Center of Innovation and Research in Materials and Polymers (CIRMAP), University of Mons - UMONS, Place du Parc 20, 7000 Mons, Belgium.
authors.forename: Philippe
authors.initials: P
authors.lastname: Dubois
authors.affiliation: Laboratory of Therapeutic Chemistry and Pharmacognosy, Faculty of Medicine and Pharmacy, University of Mons - UMONS, Place du Parc 20, 7000 Mons, Belgium(1); Research Institute for Health Sciences and Technology and Research Institute for Biosciences, Belgium.
authors.forename: Pierre
authors.initials: P
authors.lastname: Duez
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods; D003474:Curcumin / Q000737:chemistry; D044950:Flavanones / Q000737:chemistry; D005663:Furans / Q000737:chemistry; D006860:Hydrogen Bonding; D007529:Isoflavones / Q000737:chemistry; D054802:Molecular Imprinting; D058105:Polymerization; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D011794:Quercetin / Q000737:chemistry*; D052616:Solid Phase Extraction; D012997:Solvents / Q000737:chemistry
chemical_list: D044950:Flavanones; D005663:Furans; D007529:Isoflavones; D011108:Polymers; D012997:Solvents; C018674:tetrahydrofuran; C004742:daidzein; D011794:Quercetin; C005273:naringenin; D003474:Curcumin
keywords: Allium cepa; Flavonoids; Molecularly imprinted polymers; Plant extract; Quercetin; Solid-phase extraction