Cooperative binding and stabilization of the medicinal pigment curcumin by diamide linked γ-cyclodextrin dimers: a spectroscopic characterization

J Phys Chem B. 2011 Feb 10;115(5):1268-74. doi: 10.1021/jp1096025. Epub 2010 Dec 31.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Curcumin / chemistry*
  • Diamide / chemistry*
  • Dimerization
  • Hydrogen-Ion Concentration
  • Magnetic Resonance Spectroscopy
  • Micelles
  • Quantum Theory
  • Spectrometry, Fluorescence
  • gamma-Cyclodextrins / chemistry*

Substances

  • Micelles
  • gamma-Cyclodextrins
  • Diamide
  • Curcumin
  • gamma-cyclodextrin