Stability profiling of anti-malarial drug piperaquine phosphate and impurities by HPLC-UV, TOF-MS, ESI-MS and NMR

Abstract

Background: Piperaquine, 1,3-bis-[4-(7-chloroquinolyl-4)-piperazinyl-1]-propane, is an anti-malarial compoun belonging to the 4-Aminoquinolines, which has received renewed interest in treatment of drug resistant falciparu malaria in artemisinin-based combination therapy with dihydroartemisinin. The impurity profile of this drug produc is paid an ever-increasing attention. However, there were few published studies of the complete characterization o related products or impurities in piperaquine phosphate bulk and forced degradation samples Methods: The impurities in piperaquine phosphate bulk drug substance were detected by a newly develope gradient phase HPLC method and identified by TOF-MS and ESI-MS. The structures of impurities were confirmed b NMR. Forced degradation studies were also performed for the stability of piperaquine phosphate bulk drug sample and the specificity of the newly developed HPLC method. In silico toxicological predictions for these piperaquin phosphate related impurities were made by Toxtree® and Derek® Results: Twelve impurities (imp-1-12) were detected and identified, of which eight impurities (imp-1, 2, 4, 6-10 were first proposed as new related substances. Based on TOF-MS/ESI-MS and NMR analysis, the structures of imp-2 6 and 12 were characterized by their synthesis and preparation. The possible mechanisms for the formation o impurities were also discussed. These piperaquine phosphate related impurities were predicted to have a toxicit risk by Toxtree® and Derek® Conclusions: From forced degradation and bulk samples of piperaquine phosphate, twelve compounds wer detected and identified to be piperaquine phosphate related impurities. Two of the new piperaquine phosphat related substances, imp-2 and imp-6, were identified and characterized as 4-hydroxy-7-chloro-quinoline and piperaquine oxygenate with a piperazine ring of nitrogen oxide in bulk drug and oxidation sample, respectively The MS data of imp-1, 2, 4, 6-10 were first reported. The in-silico toxicological prediction showed a toxicity risk fo piperaquine related impurities by Toxtree® and Derek®.