Cocrystal of curcumin with 4,4′-bipyridine toward improved dissolution: Design, structure analysis, and solid-state characterization

The prime active ingredient of the herb curcuma longa , curcumin (CUR) has extensive pharmacological activities and high security. However, the low solubility severely restricts its investigation and application as a drug. In this paper, a new cocrystal, CUR–BPY, assembled by CUR and BPY (4,4′-bipyridine) has been synthesized and characterized by various analytical methods. Single-crystal X-ray diffraction reveals that CUR–BPY contains a pentameric BPY–CUR–BPY–CUR–BPY supramolecular architecture connected by O H⋯N hydrogen bonds and further extended to give a 1D loop-like chain through aromatic interactions. Powder dissolution experiment reveals that CUR–BPY exhibits obvious spring phenomenon and about 7 times higher apparent solubility than that of raw curcumin. The improved dissolution performance should be ascribed to the careful selection of BPY coformer and expected O H⋯N weak hydrogen bonding in CUR-BPY cocrystal.