title: Color polymorphs of aldose reductase inhibitor epalrestat: configurational, conformational and synthon differences.
abstract: 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).
authors.affiliation: School of Chemistry, University of Hyderabad, Prof. C. R. Rao Road, Central University P.O., Hyderabad 500 046, India. ashwini.nangia@gmail.com.
authors.forename: Battini
authors.initials: B
authors.lastname: Swapna
authors.affiliation: School of Chemistry, University of Hyderabad, Prof. C. R. Rao Road, Central University P.O., Hyderabad 500 046, India. ashwini.nangia@gmail.com.
authors.forename: Kuthuru
authors.initials: K
authors.lastname: Suresh
authors.affiliation: School of Chemistry, University of Hyderabad, Prof. C. R. Rao Road, Central University P.O., Hyderabad 500 046, India. ashwini.nangia@gmail.com.
authors.forename: Ashwini
authors.initials: A
authors.lastname: Nangia