Physicochemical characterizations and dissolution behavior of curcumin and α-cyclodextrin molecular inclusion complexes

The aim of present work was to enhance the aqueous solubility and dissolution rate of the curcumin, a water insoluble yellow colored phenolic pigment with good anti-inflammatory property obtained from dried rhizomes of plant Cucrcuma longa. This paper presents physicochemical evaluations of curcumin and its molecular inclusion complexes with α-cyclodextrin. Phase solubility studies revealed linear relationships (AL type) indicating 1:1 ratios of curcumin and α-cyclodextrin. Based upon the stoichiometric ratio as obtained from phase solubility studies, solid inclusion complexes were prepared by grinding, kneading and freeze drying methods and then investigated by differential scanning calorimetry (DSC), infra red spectroscopy (IR) and X-ray diffractometry (XRD). All tested curcumin complexes behaved as amorphous solid mixture in XRD and FT IR investigations. Prepared inclusion complexes were compared with pure curcumin for their dissolution behavior. Dissolution study revealed 10.5% release of curcumin at 1 hour and a maximum of 40.9% release was obtained by the end of 6 hours, which was due to poor water solubility of curcumin. In contrast, curcumin complexes demonstrated faster and better release behaviors. At least 3 fold increases in dissolution of all tested complexes were observed at one hour as compared to pure curcumin, with a maximum increase of approximately 3.5 fold as shown by kneaded and freeze dried complexes. At the end of 6 hours, approximately 60-65% release was observed from all inclusion complexes with a maximum release of 65% exhibited by freeze dried complex. Cyclodextrin complexation of curcumin enhanced dissolution of practically insoluble curcumin.