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Tautomeric polymorphism of the neuroactive inhibitor kynurenic acid
Author(s) -
Pogoda Dorota,
Janczak Jan,
Pawlak Sylwia,
Zaworotko Michael,
Videnova-Adrabinska Veneta
Publication year - 2019
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229619005990
Subject(s) - kynurenic acid , tautomer , polymorphism (computer science) , chemistry , pharmacology , medicine , biochemistry , genotype , stereochemistry , amino acid , gene , tryptophan
Kynurenic acid (KYN; systematic name: 4‐hydroxyquinoline‐2‐carboxylic acid, C 10 H 7 NO 3 ) displays a therapeutic effect in the treatment of some neurological diseases and is used as a broad‐spectrum neuroprotective agent. However, it is understudied with respect to its solid‐state chemistry and only one crystal form (α‐KYN·H 2 O) has been reported up to now. Therefore, an attempt to synthesize alternative solid‐state forms of KYN was undertaken and six new species were obtained: five solvates and one salt. One of them is a new polymorph, β‐KYN·H 2 O, of the already known KYN monohydrate. All crystal species were further studied by single‐crystal and powder X‐ray diffraction, thermal and spectroscopic methods. In addition to the above methods, differential scanning calorimetry (DSC), in‐situ variable‐temperature powder X‐ray diffraction and Raman microscopy were applied to characterize the phase behaviour of the new forms. All the compounds display a zwitterionic form of KYN and two different enol–keto tautomers are observed depending on the crystallization solvent used.