Color polymorphs of aldose reductase inhibitor epalrestat: configurational, conformational and synthon differences

We report five crystalline polymorphs and an amorphous phase of epalrestat together with configurational isomerism and color behavior: form I (deep red), form II (deep orange), form III (bright yellow), form IV (yellow), and form V (orange) are in the E , Z configuration of the drug, and a Z , Z iso...

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Bibliographic Details
Published in:Chemical communications (Cambridge, England) England), 2016-03, Vol.52 (21), p.437-44
Main Authors: Swapna, Battini, Suresh, Kuthuru, Nangia, Ashwini
Format: Article
Language:English
Subjects:
Color
Conversion
Crystal structure
Pathways
Slurries
Solvents
Stability
Transformations
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Summary:We report five crystalline polymorphs and an amorphous phase of epalrestat together with configurational isomerism and color behavior: form I (deep red), form II (deep orange), form III (bright yellow), form IV (yellow), and form V (orange) are in the E , Z configuration of the drug, and a Z , Z isomer (bright yellow). Two pathways are identified for polymorph conversion: direct transformation of the E , Z isomer and another pathway via the Z , Z isomer to the E , Z polymorphs. From a pharmaceutical perspective, the stability of polymorphs was established under grinding, solvent slurry and thermal conditions: form I (thermodynamic) > form II > form V > form III > form IV (least stable). Color polymorphs of aldose reductase inhibitor epalrestat also exhibit configurational, conformational and synthon differences. Form I is the stable modification under temperature and humidity conditions.
ISSN:1359-7345
1364-548X
DOI:10.1039/c6cc00697c