Preparation and characterization of the inclusion complex of hypocrellin A with hydroxypropyl-β-cyclodextrin

Hypocrellin A (HA) is a naturally occurring perylenequinone pigment with bright red colour. The inclusion complex of HA with hydroxypropyl-β-cyclodextrin was prepared successfully by lyophilization method for the first time. Phase solubility studies indicated that the inclusion complex was formed with possible stoichiometry of 1:1. The apparent stability constants and the thermodynamic parameters such as enthalpy change (∆H), entropy change (∆S) and Gibbs free energy (∆G) were calculated in the range of 25–45 °C. The values of apparent stability constants decrease with the increasing of temperature. The thermodynamic results showed that the inclusion process was an exothermic and enthalpy-driven process accompanied with a negative entropic contribution. The formation of inclusion complex was also conformed by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetry and spectroscopic studies. The inclusion complex showed much better water solubility and dissolution property than the free HA. Therefore, the inclusion complex can be used to expand the application of HA in food, feed and pharmaceutical industries.