MOLECULAR CHARACTERIZATION OF TRANS FERULIC ACID: β-CYCLODEXTRIN INCLUSION COMPLEX. EXPERIMENTAL AND THEORETICAL APPROACH

The formation of inclusion complex between beta-cyclodextrin (beta-CD) and the trans-ferulic acid (t-FA) has been investigated both in solution and in the solid state. Solution-state complexation between the t-FA and beta-CD was established using isothermal titration calorimetry (ITC), 1H NMR and UV spectroscopy. The thermodynamic parameters Delta H, Delta S and Delta G obtained using ITC provide insights into the driving forces involved during complex formation. Thermodynamic analysis suggests a hydrophobic interaction associated with the displacement of water from the cavity of the beta-CD by the t-FA. From the 1H NMR spectroscopic studies 1:1 complex stoichiometry was indicated and association constant (K) was determined as 4.39 x 103 M-1 for the complex t-FA:beta-CD. Solid-state supramolecular complex, in 1:1 molar ratio was obtained by freeze-drying and investigated by PXRD, FTIR and DSC. The changes highlighted by these methods used for the analysis, relative to the starting compounds, suggest the presence of interactions between them and the formation of the complex in the solid state. A molecular docking study added an additional insight to the experimental analysis regarding the binding conformation ofAt-FA to beta-CD. The antioxidant activity of the inclusion complex was evaluated using the ferric reducing antioxidant power (FRAP) assay, compared to free ferulic acid, indicating it has the same intensity in the endpoint of the assay, but with a retardation effect in time due to inclusion.