Tautomeric polymorphism of the neuroactive inhibitor kynurenic acid

Dorota Pogoda, Jan Janczak, Sylwia Pawlak, Michael Zaworotko, Veneta Videnova-Adrabinska

Research output: Contribution to journalArticlepeer-review

Abstract

Kynurenic acid (KYN; systematic name: 4-hydroxyquinoline-2-carboxylic acid, C10H7NO3) 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 (β-KYN.H2O) 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.H2O, 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.

Original languageEnglish
Pages (from-to)793-805
Number of pages13
JournalActa Crystallographica Section C: Structural Chemistry
Volume75
DOIs
Publication statusPublished - 1 Jun 2019

Keywords

  • Crystal structure
  • Hirshfeld surface analysis
  • Hydrogen bonding
  • Keto-Enol tautomers
  • Kynurenic acid
  • Molecular drug
  • Neuroactive inhibitor
  • Polymorphism
  • Trypto-phan metabolite

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