Preparation and release behaviour of the inclusion complexes of phenylethanol with β‐cyclodextrin

Abstract

The formation of the inclusion complexes between two phenylethanol isomers [1‐phenylethanol (1‐PE) and 2‐PE)] and three cyclodextrins namely α‐cyclodextrin (α‐CD), β‐cyclodextrin (β‐CD) and HP‐β‐cyclodextrin (HP‐β‐CD) was studied. Phase‐solubility studies showed the two isomers formed 1:1 stoichiometric inclusion complexes with these cyclodextrins and the aqueous solubility of 1‐PE and 2‐PE significantly increased with increasing the cyclodextrin concentration. In this study, β‐CD was chosen as a host molecule, and solid inclusion complexes of β‐CD with two phenylethanol isomers were prepared via the co‐precipitation method for the enhancement of their thermal stability and sustained release. The presence of the two isomers in the inclusion complexes was confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H‐NMR) spectra. X‐ray powder diffraction (XRD) results indicated new crystalline phases for the inclusion complexes. Differential scanning calorimetry (DSC) studies for the inclusion complexes have also shown the formation of supramolecular inclusion complexes between β‐CD and the two isomers. Thermogravimetric analysis (TGA) results demonstrated that the thermal stability of the two isomers was increased as a result of the formation of the inclusion complexation with β‐CD. The release study suggested that β‐CD provided protection for 1‐PE and 2‐PE against evaporation, and 1‐PE in the inclusion complex had a lower release rate than that of 2‐PE. The results have been confirmed with PM3 and B3LYP/6‐31G(d) calculation. It indicates that β‐CD is a proper wall material for increasing thermal stability and the controlled release of 1‐PE and 2‐PE. Copyright © 2015 John Wiley & Sons, Ltd.

Host‐guest complexes of estragole with β‐cyclodextrin: an experimental and theoretical investigation

“…The result indicated LC reached 93 mg of ES/g of inclusion complexes with EE of 56.8%, which agrees with the previously reported data . LC and EE values for ES were lower compared with the data from other kinds of guest components, which may be because of its very low aqueous solubility …”

“…The inclusion complex is an effective way to control the release of guest molecules. In earlier studies, the release of the guests depended markedly upon the environmental RH and temperature. In the present study, release profiles of ES from the ES/β‐CD inclusion complexes at 40, 60, 80 and 100 °C at 75 ± 1% RH are shown in Fig.…”

“…The release characterisation of the ES/β‐CD inclusion complex at a temperature range from 40 to 100 °C was determined according to the method described by Yang et al . . Approximately 1 g of the inclusion complexes was placed in a controlled temperature and humidity chamber.…”

“…Avrami's equation is commonly used to describe the kinetics of controlled release, which was originally applied as a mathematic model for the different mechanisms of crystallization . Some encapsulated EOs have been studied for release kinetics using Avrami's equation . Avrami's equation can be expressed as: where, Y is the release fraction of ES during release at time t , k is the release rate constant, and n is the Avrami parameter or release mechanism.…”

Interactions between Bio-Based Compounds and Cyclodextrins

“…Another interesting approach to learn about the formation of host-guest complexes, in solid state, is to study the release kinetics of the EO. These studies, although do not allow to quantify the total amount of EO incorporated into the CDs, are of utmost importance to evaluate the presence of the EO in the complex as well as to provide hints on the release mechanism; the latter is quite relevant for EOs used as fragrances [91,92].…”