Solid inclusion complex of terpinen-4-ol/β-cyclodextrin: kinetic release, mechanism and its antibacterial activity

Terpinen-4-ol has several biological properties, but its low stability and water-solubility limit its use. This study reports the formation of a solid terpinen-4-ol/-cyclodextrin (-CD) inclusion complex via lyophilization. Release experiments were performed at various temperatures (40, 60, 80, and 100 degrees C) with humidity of 70%. The release of terpinen-4-ol was significantly increased with rising temperature. Avrami's equation was used to analyse release kinetics and a good fit was observed for terpinen-4-ol release. In addition, the complex enhanced antibacterial activity against Staphylococcus aurueus, Pseudomonas aeruginosa and Escherichia coli, with concentration ranging from 1.25 mg/ml to 5 mg/ml. To explain the experimental data, physico-chemical techniques have been utilized to investigate the inclusion complex of terpinen-4-ol with -CD. Finally, the possible structure of the complex was proposed by quantum chemical calculations. The results indicated that enhanced thermal stability and antibacterial activity of terpinen-4-ol could be attributed to the weak interactions of hydrogen bonds between terpinen-4-ol and -CD. Copyright (c) 2014 John Wiley & Sons, Ltd.