Synthesis and structural characterization of cocrystals of isoniazid and cinnamic acid derivatives

Isoniazid is a key antitubercular agent which exhibits poor chemical stability in the solid state. Cocrystallization with hydroxyl derivatives of cinnamic acid, which themselves possesses antitubercular and antioxidant activity, may produce solid forms with improved pharmaceutical properties. The complementary nature of the functional groups of isoniazid and the chosen coformers resulted in a high success rate for cocrystal formation. The three previously unknown cocrystal forms, plus a new polymorph were characterized by solid-state NMR, DSC, PXRD and single crystal XRD. Three previously known cocrystals were also synthesized and characterized. NMR chemical shifts were observed to distinguish between a key synthon involving the carboxylic acid of cinnamic acid. (C) 2020 Elsevier B.V. All rights reserved.