A comprehensive cocrystal study for the insoluble natural pharmaceutical compound xanthotoxin (XT) was conducted, in which xanthotoxin-para aminobenzoic acid (XT-PABA) and xanthotoxin-oxalic acid (XT-OA) cocrystals were obtained. The xanthotoxin cocrystals were characterized by powder X-ray diffraction, thermal analysis, and FT-IR spectra, and the crystal structures were determined by single-crystal X-ray diffraction. Crystal structures and thermal analysis showed that XT-OA was more stable than XT-PABA. Energy framework calculation indicated that H-bond and π···π interactions generated in XT-OA were stronger than that in XT-PABA and xanthotoxin. The powder dissolution experiments of xanthotoxin and its cocrystals suggested the XT-OA cocrystal might be applied as an alternative formulation of API, on account of its enhanced solubility and stability in the hydrochloric acid buffer solution (pH 1.2). The cocrystallization engineering can prolong the enhanced apparent solubility via modulating the stability.
Keywords: Cocrystals; Crystal structure; Solubility; Stability; Xanthotoxin.
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