INTERACTIONS BETWEEN P-HYDROXYBENZOIC ACID-ESTERS AND HYDROXYPROPYL-BETA-CYCLODEXTRIN AND THEIR ANTIMICROBIAL EFFECT AGAINST CANDIDA-ALBICANS

The interactions between hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and a series of PHB esters were studied in aqueous solution by solubility isotherms and in the solid state by thermal analysis (DSC) and X-ray diffractometry. Calculated complex constants show different stabilities of the inclusion complexes formed. The antimicrobial effect against Candida albicans was tested and MIC values were ascertained. It was found that the antimicrobial activity of the preservatives against the test organism was reduced in the presence of HP-beta-CD. QSAR analyses were made to describe this effect by physicochemical parameters such as lipophilicity or complex stability constants. The results suggest that the degree of inactivation is completely dependent on the complex bonded fraction of the PHB ester.