High-pressure NMR characterization of triacetyl-β-cyclodextrin in supercritical carbon dioxide

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Cyclodextrins are used in many drug formulations since their cavities provide microenvironments where drug molecules can enter and form inclusion complexes for controlled drug delivery. Supercritical carbon dioxide (scCO 2) is an alternative to organic solvents and a very attractive medium for the preparation of these inclusion complexes. The potential ability of triacetyl-β-cyclodextrin (TA-β-CD) to form inclusion complexes in addition to its high miscibility in liquid and scCO2 could offer a chance for an economical and environmental friendly chemical processing. In this work, high-pressure NMR studies were performed in order to obtain information on the molecular structure and dynamics of TA-β-CD in scCO2 at 313.15 K and 20 MPa and its ability to form inclusion complexes under these conditions was studied. The influence of scCO2 on a number of NMR spectral parameters, such as chemical shifts, spin-spin coupling constants, nuclear Overhauser effect (NOE) and spin-lattice relaxation (T1) has been studied. We unequivocally show for the first time structural changes of TA-β-CD in scCO2, like acetyl chain orientation and overall shape distortions that can affect its inclusion capability in this medium. The possibility of cavity self-closure is discussed and the results of two inclusion studies that support cavity self-closure, with the angiotensin-converting enzyme inhibitor, captopril, and the nonsteroid anti-inflammatory drug, flufenamic acid, are presented.

Original languageEnglish
Pages (from-to)133-141
Number of pages9
JournalMagnetic Resonance in Chemistry
Issue number2
Publication statusPublished - 1 Feb 2009


  • H
  • Captopril
  • Flufenamic acid
  • Host-guest complexes
  • NMR
  • Nuclear Overhauser effect
  • Per-acetylated-β-cyclodextrin
  • Relaxation
  • Supercritical CO


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