title: Cooperative binding and stabilization of the medicinal pigment curcumin by diamide linked γ-cyclodextrin dimers: a spectroscopic characterization.
abstract: Diamide linked γ-cyclodextrin (γ-CD) dimers are used to capture curcumin and suppress its decomposition in water. In this study, succinamide and urea linked γ-CD dimers joined through the C6(A) carbon on each γ-CD are used. The γ-CD dimers, 66γCD(2)su and 66γCD(2)ur, show a remarkable ability to suppress the decomposition of curcumin and extend its half-life from less than 30 min to greater than 16 h. The 1:1 association of curcumin with 66γCD(2)su and 66γCD(2)ur has high stability constants of 8.7 × 10(6) M(-1) and 2.0 × 10(6) M(-1), respectively. In addition, 2D (1)H NOESY NMR results show specific hydrogen interactions in the association of curcumin with 66γCD(2)su and 66γCD(2)ur, consistent with the cooperative binding of curcumin by both γ-CD annuli of 66γCD(2)su and 66γCD(2)ur. The interactions between curcumin in the linked γ-CD dimers and surfactant micelles were studied using fluorescence spectroscopy. While linked γ-CD dimer-bound curcumin has a negligible fluorescence quantum yield, a significant increase in fluorescence intensity (Φ(fl) > 2%) in the presence of micelles suggests that curcumin is delivered to the micelle. The overall results indicate that the diamide linked γ-CD dimers are highly promising systems for curcumin delivery in vivo due to effective curcumin stabilization.
authors.affiliation: Department of Chemistry, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Harada
authors.forename: Duc-Truc
authors.initials: DT
authors.lastname: Pham
authors.forename: Mandy H M
authors.initials: MH
authors.lastname: Leung
authors.forename: Huy Tien
authors.initials: HT
authors.lastname: Ngo
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Lincoln
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Easton
authors.forename: Tak W
authors.initials: TW
authors.lastname: Kee
mesh_terms: D003474:Curcumin / Q000737:chemistry*; D003958:Diamide / Q000737:chemistry*; D019281:Dimerization; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D047408:gamma-Cyclodextrins / Q000737:chemistry*
chemical_list: D008823:Micelles; D047408:gamma-Cyclodextrins; D003958:Diamide; D003474:Curcumin; C023792:gamma-cyclodextrin