Study on Supramolecular Systems of Cyclodextrins and Magnolol, Honokiol by Thin Layer Chromatography

The interactions between magnolol, honokiol and six cyclodextrins (CDs) have been studied by reversed-phase thin-layer chromatography. The NH 3 H 2 O-NH 4 Cl buffer containing various CDs (pH 9.7, 20C) and polyamide plate are selected, respectively, as mobile and stationary phases. CDs except for f -CD and CM- g -CD can form inclusion complex with magnolol. However, the strong space resistance between honokiol and CD makes it difficult for them to form inclusion complex. The comparison of inclusion capacity of different CDs indicates that for the ionic CDs the charge interaction plays an important role in the inclusion procedure. The thermodynamic parameters of interaction imply that the inclusion process shows the enthalpy-entropy compensation effect. The j H - T j S plot for CDs displays an excellent linear relationship, affording a very large slope ( f =1.1) and intercept ( T j S 0 0 =16.3), which exhibits that the enthalpic gain from the inclusion complexation is completely canceled out by the entropic loss from the conformational changes caused upon guest inclusion. The marked influence of CDs on the hydrophobicity of magnolol suggests that this interaction may modify the biological properties of magnolol.

Keywords:

• Cyclodextrin
• Reversed-phase Thin-layer Chromatography
• Magnolol
• Honokiol Supramolecular System
• Enthalpy-entropy Compensation Effect