Interaction of Cyclodextrins with Oily Substances

Abstract

Inclusion of ƒ¿-cyclodextrin (ƒ¿-CD), ƒÀ-cyclodextrin (ƒÀ-CD), and ƒÁ-cyclodextrin (ƒÁ-CD), which can effect a reduction of oily substances, was investigated with a view to constructing low-fat substances through this interaction. The oily substances used were cholesterol, triolein, and four saturated fatty acids having different alkyl chain lengths; namely, lauric, myristic, palmitic, and stearic acids, as well as oleic acid, an unsaturated fatty acid. Each oily substance was dissolved in ethanol, while the CDs were dissolved in water. Thereafter, inclusion was carried out by mixing each oily substance solution with a CD solution. Using a water-ethanol solvent, interaction between each water-soluble CD and the oily substances was examined. Inclusion of an oily substance was determined by a thin-layer chromatograph with hydrogen flame ionization detector (TLC-FID). ƒ¿-CD did not form an inclusion compound with cholesterol and triolein, but did with oleic acid. ƒÀ-CD formed a compound with cholesterol, although the amount of ƒÀ-CD involved was low, owing to poor solubility in water. ƒÁ-CD formed inclusion compounds with oleic acid, cholesterol, and triolein. CDs thus demonstrated selective inclusion of oily substances. In the case of ƒ¿-CD and fatty acids, the amount of saturated inclusion and the binding coefficient increased with increasing chain length of the fatty acid, forming more stable inclusion compounds as the chain length became longer. On the other hand, the amount of saturated inclusion by ƒÀ-CD of cholesterol was low because ƒÀ-CD has low solubility in water, but the binding coefficient was large and the