Abstract
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
Highlights
Curcumin is a natural yellow compound found in turmeric (Curcuma longa L.)
We evaluated the effect of the curcumin-cyclodextrin inclusion complex preparation method on the solubility and stability of curcumin
We evaluated four types of CDs including three natural α, β, and γ-CD and one derivative hydroxypropyl (HP)-β-CD on curcumin solubility based on a phase solubility study and selected one CD that gave the best result for preparation of inclusion complexes with curcumin
Summary
Curcumin is a natural yellow compound found in turmeric (Curcuma longa L.). it has shown many excellent pharmacological activities in in vitro experiments such as antioxidant, antiinflammatory, anti-microbial and anti-tumor activities [1,2,3,4], curcumin has not yet been approved for use as a drug due to the very low bioavailability obtained after curcumin oral administration, which is due, in part, to poor solubility (11 ng/mL in aqueous buffer, pH 5.5 [5]) and stability (t1/2 of curcumin in PBS pH 7.2, < 10 min [6]). We evaluated the effect of the curcumin-cyclodextrin inclusion complex preparation method on the solubility and stability of curcumin. We evaluated four types of CDs including three natural α-, β-, and γ-CD and one derivative hydroxypropyl (HP)-β-CD on curcumin solubility based on a phase solubility study and selected one CD that gave the best result for preparation of inclusion complexes with curcumin. The dried sample was sieved and the resulting inclusion complex sample kept under the same conditions as that prepared by common solvent evaporation. The excessive amount of each inclusion complex (~ 50 mg) and curcumin was separately placed in a 5-mL glass vial containing 1 mL of distilled water and stirred for 24 h at 25 ± 1 oC until a saturated solution was obtained.
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