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

PURPOSE: 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. METHODS: 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. RESULTS: The apparent stability constants were found to be 117 dm3 mol-1 for the complex with ß-CD and 161 dm3 mol-1 for the complex with (2-hydroxypropyl)-ß-cyclodextrin (HP-ß-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-ß-CD, and 1.27 µg cm-3 for inclusion complex with ß-CD. CONCLUSION: 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.

Preparation, characterization and antimicrobial activity of inclusion complex of biochanin A with (2-hydroxypropyl)-ß-cyclodextrin.

OBJECTIVES: An inclusion complex of biochanin A (BCA) with (2-hydroxypropyl)-ß-cyclodextrin (HP-ß-CD) was prepared in the ethanol solution to improve its water solubility. METHODS: Using the FTIR, 1 H-NMR, XRD, DSC and SEM methods, the structural characterization of the prepared complex was analysed. KEY FINDINGS: The phase-solubility study has shown that the solubility of BCA was increased twofold in 42% (v/v) ethanol solution after complexation with HP-ß-CD. The complex between BCA and HP-ß-CD was prepared in the molar ratio of 1 : 1. The antibacterial activity of the inclusion complex was investigated against the various bacteria, fungus and yeast using the microdilution method. The minimal inhibitory concentration values for the analysed strain of bacteria were in the range of 0.84-1.69 mg/cm3 , whereby the prepared inclusion complex exhibited less effect on the reduction of the number of Escherichia coli and Klebsiella pneumoniae species compared to pure BCA. The inclusion complex of BCA was significantly more active against Candida albicans than pure BCA. Biochanin A and its inclusion complex has not expressed the activity against Aspergillus niger. CONCLUSIONS: Based on the obtained results, it can be concluded that the antimicrobial activity of BCA was remained unchanged after complexation.