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

MIHAELA MIC 1, ADRIAN PÎRNĂU 1*, CĂLIN G. FLOARE 1, MARIA O. MICLĂUS 1, IRINA KACSO 1, BIANCA M TIHĂUAN 2,3, MĂDĂLINA AXINIE (BUCOS) 3,4, GABRIEL MARC 5, OVIDIU ONIGA 5, OVIDIU CRIȘAN 6

1 National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat, 400293, Cluj- Napoca, Romania
2 Research Institute of the University of Bucharest – ICUB, 91-95 Splaiul Independentei, 50567, Bucharest, Romania
3 Research & Development for Advanced Biotechnologies and Medical Devices, SC Sanimed International Impex SRL, Călugăreni, Romania
4 Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, 011061 Bucharest, Romania
5 Department of Pharmaceutical Chemistry, Faculty of Pharmacy, “Iuliu Hațieganu” University of Medicine and Pharmacy, 41 Victor Babeș Street, 400012, Cluj-Napoca, Romania
6 Department of Organic Chemistry, Faculty of Pharmacy, “Iuliu Hațieganu” University of Medicine and Pharmacy, 41 Victor Babeș Street, 400012, Cluj-Napoca, Romania

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The formation of inclusion complex between β-cyclodextrin (β-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 β-CD was established using isothermal titration calorimetry (ITC), 1H NMR and UV spectroscopy. The thermodynamic parameters ΔH, ΔS and ΔG 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 β-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:β-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 of t-FA to β-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.