American Chemical Society
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Approach of Cocrystallization to Improve the Solubility and Photostability of Tranilast

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posted on 2013-08-07, 00:00 authored by Na Geng, Jia-Mei Chen, Zi-Jian Li, Long Jiang, Tong-Bu Lu
The cocrystals and salts of an antiallergic drug, tranilast, were synthesized to improve its solubility and photostability. Two tranilast cocrystals with urea (1) and nicotinamide (2), as well as two salts with cytosine (3) and sodium ion (4), were obtained and characterized by infrared spectra, thermogravimetric analyses, differential scanning calorimetry, and powder and single crystal X-ray diffractions. The results of single crystal structure analyses of 13 indicate that tranilast combines amide groups in coformers via R22(8) synthon, resulting in a 1:1 stoichiometry. The complexes showed advantages in terms of solubility and photostability in comparison to pure tranilast. The maximum solubility values of 13 in phosphate buffer of pH 6.8 are approximately 1.6, 1.9, and 2.0 times as large as that of tranilast, and the residual of tranilast is 79.5, 92.9, 88.5, 86.2, and 87.4% for tranilast and 14, respectively, under the fluorescent lamp irradiation for 96 h.