Purpose:  To prepare and characterize inclusion complex of berberine hydrochloride with hydroxypropyl-β-cyclodextrin in order to achieve enhanced solubility and reduced bitterness of the former.

Methods: The inclusion complex of berberine hydrochloride with hydroxypropyl-β-cyclodextrin (1:1) was prepared by freeze-drying method and compared with the the physical mixtures of the compounds. Inclusion complexation was studied by phase solubility diagram, differential thermal analysis, spectrophotometric characterization and dissolution rate. The solubility of the formulations was evaluated by saturation solubility studies while their bitterness was tested in human volunteers.

Results: Differential thermal analysis and spectrophotometric characterization indicate that berberine hydrochloride formed inclusion complex with hydroxypropyl-β-cyclodextrin. The phase solubility diagram of berberine hydrochloride with hydroxypropyl-β-cyclodextrin was of A_L-type, with a stability constant was 694.5 L/mol at 25 ^oC. The solubility of berberine hydrochloride was increased by 5.27 times for the complex at a concentration of 0.01 mol/L. The dissolution of berberine hydrochloride after 20 min from the inclusion complex, physical mixture and pure berberine hydrochloride was 89.6, 69.8 and 58.8 %, respectively. The bitterness of the inclusion complex was considerably lower than that of the drug alone or the physical mixture with hydroxypropyl-β-cyclodextrin.

Conclusion: The inclusion complex demonstrated improved dissolution properties and lowered the bitterness of berberine hydrochloride.