2-Hydroxypropylated cyclodextrins as a sustained-release carrier for fragrance materials

The potential use of three kinds of 2-hydroxypropylated cyclodextrins [HP-CyDs: 2-hydroxypropyl-alpha-cyclo dextrin (HP-alpha-CyD), 2-hydroxypropyl-beta-cyclodestrin (HP-beta-CS D) and 2-hydroxypropyl-gamma-cyclodestrin (HP-gamma-CyD)] in the solubilizing of fragrance materials and the retarding of their release rates was examined, Of the HP-CSDs, HP-beta-CyD significantly increased the solubility of six fragrance materials in water, and the apparent 1:1 stability constant of the HP-beta-CyD complexes was higher than those of the HP-alpha-CyD and HP-gamma-CyD complexes, Ultraviolet, circular dichroism and nuclear magnetic resonance spectroscopic studies suggested that the inclusion mode of eugenol is different between the HP-beta-CyD complex and the HP-alpha- or HP-gamma-CSD complexes, The release rates of ci-camphor and 3-l-methoxypropane 1,2-diol from water were remarkably decreased by the addition of HP-CyDs, where the rate of decrease was in agreement with that of the stability constant ranking of the complexes, i.e., fragrance materials alone < HP-alpha-CyD < HP-gamma-CyD < HP-beta-CyD. In order to retard the transport of fragrance materials to skin, the suppressive effect of HP-CyDs was examined in vitro. The mean transit time for eugenol through the skin barrier increased in the order of eugenol alone < HP-gamma-CyD < HP-alpha-CSD < HP-beta-CyD, and the suppressive effects of HP-alpha-CyD and HP-beta-CJ D were remarkably greater than that of the nonionic surfactant, HCO-60, The present data suggest that HP-beta-CyD has a significant advantage ol er the other HP-CyDs and HCO-60 with respect to providing high aqueous solubility and the sustained release of fragrance materials while maintaining a lack of toxicity in topical liquid preparations of fragrance materials.