Preparation of Curcumin-Piperazine Coamorphous Phase and Fluorescence Spectroscopic and Density Functional Theory Simulation Studies on the Interaction with Bovine Serum Albumin

In the present study, a new coamorphous phase (CAP) of bioactive herbal ingredient curcumin (CUR) with high solubilitythe was screened with pharmaceutically acceptable co-formers. Besides, to provide basic information for the best practice of physiological and pharmaceutical preparations of CUR-based CAP, the interaction between CUR-based CAP and bovine serum albumin (BSA) was studied at the molecular level in this paper. CAP of CUR and piperazine with molar ratio of 1:2 was prepared by EtOH-assisted grinding. The as-prepared CAP was characterized by powder X-ray diffraction, modulated temperature differential scanning calorimetry, thermogravimetric analysis, Fourier-transform infrared, and solid-state C-13 nuclear magnetic resonance. The 1:2 CAP stoichioimetry was sustained by C=O center dot center dot center dot H hydrogen bonds between the N-H group of the piperazine and the C=O group of CUR; piperazine stabilized the CAP. The dissolution rate of CUR piperazine CAP in 30% ethanol water was faster than that of CUR; the t(50) values were 243.1 min for CUR and 4.378 min for CAP. Furthermore, interactions of CUR and CUR piperazine CAP with BSA were investigated by fluorescence spectroscopy and density functional theory (DFT) calculation. The binding constants (K-b) of CUR and CUR-piperazine CAP with BSA were 10.0 and 9.1 x 10(3) L mol(-1) at 298 K, respectively. Moreover, DFT simulation indicated that the interaction energy values of hydrogen-bonded interaction in the tryptophan-CUR and tryptophan-CUR piperazine complex were-26.1 and-17.9 kJ mol(-1). respectively. In a conclusion, after formation of CUR piperazine CAP, the interaction forces between CUR and BSA became weaker.