The effect of complexation with cyclodextrins on the antioxidant and antimicrobial activity of ellagic acid

The aim of the paper was to develop the simple procedures for preparation of inclusion complexes of ellagic acid (EA) with cyclodextrins (CDs) and to investigate their antioxidant and antimicrobial activity.

The structural characterization was carried out using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) methods. The phase solubility technique was used to investigate the interactions between 'host' and 'guest' molecules and to estimate the molar ratio between them. The antioxidant and antimicrobial activity of EA and inclusion complexes were determined.

The apparent stability constants were found to be 117 dm³ mol^-1 for the complex with β-CD and 161 dm³ mol^-1 for the complex with (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD). The results of phase-solubility studies showed that EA formed the inclusion complexes with CDs in the molar ratio of 1:1. The calculated half-maximal inhibitory concentration was 41.18 μg cm^-3 for butyl hydroxy toluene, 1.96 μg cm^-3 for EA, 0.88 μg cm^-3 for inclusion complex with HP-β-CD, and 1.27 μg cm^-3 for inclusion complex with β-CD.

The stability constants indicated the rapid release of EA from the inclusion complexes in the aqueous medium at 25 °C. The antioxidant activity of EA was increased, while the antimicrobial activity was preserved after complexation with CDs.