Preparation and Characterization of Solid Complexes of Naphtoquinone and Hydroxypropyl-β-Cyclodextrin

The formation of an inclusion compound between a naphthoquinone derivative (I) and HP-ß-CD was studied in solid state by X-ray diffractometry, DSC, and IR. Introduction The formation of inclusion complexes with cyclodextrins constitutes a widely used strategy to increase the aqueous solubility and to decrease the countereffects of many drugs. Isoxazolylnaphthoquinones belong to a family of compounds with bacterial and tripanocidal activity [1,2], as well as with very low solubility in water. In previous studies in our laboratory, we demonstrated that their hydrophilic capacity increases markedly through complexation with hydroxypropyl-ß-cyclodextrin (HP-ßCD) in aqueous solution [3]. In this study we investigate the formation of complexes between 2-hydroxy-N-(3,4-dimethyl-5isoxazolyl)-1,4-naphthoquinone-4-imine (I) and HP-ß-CD in solid state. Thermoanalytic techniques, X-ray diffraction and IR spectroscopy were performed [4]. Experimental 1. Materials The synthesis and identification procedures for I have been described previously. HP-β-CD (MW = 1326 1400; degree of molar substitution, 7.0) was a gift from CERESTAR USA Inc. (Hammond, IN). All other materials and solvents were of analytical reagent grade.