Study of the solubility, stability and structure of inclusion complex of cholesterol with â-cyclodextrin.

DOS SANTOS, CRISTINA; MAZZOBRE, MARÍA FLORENCIA; BUERA, MARÍA DEL PILAR

Queretaro

Simposio; INTERNATIOPNAL SYMPOSIUM ON THE PROPERTIES OF WATER; 2010

Cyclodextrins are able to form inclusion complexes with hydrophobic molecules. As b-cyclodextrin (beta-CD) is also nontoxic provides advantages when used for removal of undesired components (such as cholesterol) present in the food in its natural form, or for improving the characteristics of many foods through their complexation with bioactive compounds. This study was carried out to determine the optimum experimental conditions (b-CD concentration, mixing temperature and time) for cholesterol encapsulation. Complex formation in solution is a dynamic equilibrium process and the stability of the complex can be described in terms of the equilibrium constant. In this work, inclusion complexes of cholesterol and b-CD were prepared and the equilibrium constant was obtained. Water sorption isotherms were also obtained. The physical properties and the stability of the complexes were dependent on the time of storage and water content. The inclusion complexes of cholesterol in b-CD were prepared by the coprecipitation method using different cholesterol/â-CD molar ratios, temperatures and stirring times. DSC was used to evaluate complex formation. Sorption isotherms of b-CD and of the complexes were obtained by the isopiestic method at 25°C. Phase solubility studies were carried out at different temperatures and the correspondent equilibrium constants were calculated. Cholesterol was partially encapsulated in b-CD depending of the experimental conditions. Nearly 70% of the initial cholesterol was encapsulated, stirring 48 hours at 30°C with a cholesterol/b-CD molar ratio 1:1. The presence of cholesterol greatly modified the b-CD sorption curves being the amount of adsorbed water smaller in the combined systems. These results confirm the complex formation at any of the studied molar ratio. The “driving force” of the complex formation is the substitution of the high-enthalpy water molecules by an appropriate guest molecule. The constants decreased with increasing temperature, as expected for an exothermic process. The limited water solubility of cholesterol could be overcome by the formation of b-CD inclusion complexes. The systems probe to be stable at different storage conditions. These data could be essential to employ cyclodextrins for removing undesired compounds from natural products (such as cholesterol from milk) or to incorporate  functional ingredients in the development of innovative food products.