Curcumin-Hydroxypropyl-β-Cyclodextrin Inclusion Complex Preparation Methods: Effect of Common Solvent Evaporation, Freeze Drying, and pH Shift on Solubility and Stability of Curcumin

Purpose: To evaluate the effect of the preparation method on the inclusion complex of curcumin and hydroxypropyl-β-cyclodextrin (HP- β -CD).
Methods: HP-β-CD was selected to prepare an inclusion complex with curcumin at a molar ratio of 1:1. The inclusion complexes were prepared using three different methods: common solvent evaporation (CSE), freeze drying (FD), and pH shift. The inclusion complexes were characterized by differential scanning calorimetry (DSC) and fourier transform infrared (FTIR) spectroscopy. The content, solubility, dissolution, and stability of the complexes were evaluated and compared with curcumin and their physical mixture.
Results: Formation of inclusion complexes was confirmed by DSC and FTIR results. CSE and FD methods gave a high content of curcumin in the inclusion complexes (> 88.39 %), while pH shift gave a lower content (64.04 %). All three methods significantly (p < 0.05) increased curcumin solubility (> 276.43-fold). However, higher stability complexes were obtained using CSE and FD methods.
Conclusion: Among the three preparation methods (CSE, FD and pH shift) used for the inclusion complexes, CSE is the most suitable method for preparation of curcumin-HP-β-CD inclusion complex for increased curcumin solubility and stability.

Keywords
Curcumin; Cyclodextrin; Inclusion complex; Solubility; Stability; Common solvent evaporation; Freeze drying; pH shift