title: The inclusion complex of rosmarinic acid into beta-cyclodextrin: A thermodynamic and structural analysis by NMR and capillary electrophoresis.
abstract: This work focuses on the characterization of the rosmarinic acid (RA)-β-cyclodextrin (CD) complex in aqueous solution by (1)H NMR (1D- and 2D-ROESY), completed with studies by capillary electrophoresis (CE). From the (1)H NMR data, the stoichiometry of the complex was determined by a Job's plot and the binding constant was estimated from a linear regression (Scott's method). At pH 2.9, the results showed that RA binds CD with a 1:1 stoichiometry and a binding constant Kb of 445 (±53) M(-1) or 465 (±81) M(-1) depending on the CD protons (H-5 or H-3) selected for the evaluation. The Kb value was also calculated from the CD-induced chemical shifts of each RA proton in order to collect information on the structure of the complex. The pH dependence of Kb revealed that the RA carboxylic form displays the highest affinity for CD. An investigation by capillary electrophoresis fully confirmed these results. 2D ROESY analysis provided detailed structural information on the complex and showed a strong correlation between H-3 and H-5 of CD and most RA protons. In conclusion, RA, an efficient phenolic antioxidant from rosemary with a marketing authorization, spontaneously forms a relatively stable inclusion complex with CD in water.
authors.affiliation: University of Avignon, INRA, UMR408 SQPOV, 84000 Avignon, France.
authors.forename: Amra
authors.initials: A
authors.lastname: Aksamija
authors.affiliation: University of Avignon, UMR5247 CBSA, 84000 Avignon, France.
authors.forename: Ange
authors.initials: A
authors.lastname: Polidori
authors.affiliation: University of Avignon, INRA, UMR408 SQPOV, 84000 Avignon, France.
authors.forename: Raphaël
authors.initials: R
authors.lastname: Plasson
authors.affiliation: University of Avignon, INRA, UMR408 SQPOV, 84000 Avignon, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Dangles
authors.affiliation: University of Avignon, INRA, UMR408 SQPOV, 84000 Avignon, France. Electronic address: valerie.tomao@univ-avignon.fr.
authors.forename: Valérie
authors.initials: V
authors.lastname: Tomao
mesh_terms: D002934:Cinnamates / Q000737:chemistry*; D053630:Depsides / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons; D013816:Thermodynamics; D047392:beta-Cyclodextrins / Q000737:chemistry*; D000097123:Rosmarinic Acid
chemical_list: D002934:Cinnamates; D053630:Depsides; D011522:Protons; D047392:beta-Cyclodextrins; D000097123:Rosmarinic Acid
keywords: Beta-cyclodextrin; Capillary electrophoresis; Inclusion complex; NMR; ROESY; Rosmarinic acid