title: Use of LC-MS/TOF, LC-MS(n), NMR and LC-NMR in characterization of stress degradation products: Application to cilazapril.
abstract: Forced degradation studies on cilazapril were carried out according to ICH and WHO guidelines. Significant degradation of the drug was observed in acid and base conditions, resulting primarily in cilazaprilat. In neutral condition, five degradation products were formed, while under oxidative condition, two degradation products were generated. In total, seven degradation products were formed, which were separated on an Inertsil C-18 column using a stability-indicating HPLC method. Structure elucidation of the degradation products was done by using sophisticated and hyphenated tools like, LC-MS/TOF, LC-MS(n), on-line H/D exchange, LC-NMR and NMR. Initially, comprehensive mass fragmentation pathway of the drug was laid down. Critical comparison of mass fragmentation pathways of the drug and its hydrolytic degradation products allowed structure characterization of the latter. 1D and 2D proton LC-NMR studies further confirmed the proposed structures of hydrolytic degradation products. The oxidative degradation products could not be characterized using LC-MS and LC-NMR tools. Hence, these degradation products were isolated using preparative HPLC and extensive 1D ((1)H, (13)C, DEPT) and 2D (COSY, TOCSY, HETCOR and HMBC) NMR studies were performed to ascertain their structures. Finally, degradation pathways and mechanisms of degradation of the drug were outlined.
authors.affiliation: Biocon-BMS R&D Centre (BBRC), Biocon Park, Bangalore, India.
authors.forename: Mallikarjun
authors.initials: M
authors.lastname: Narayanam
authors.affiliation: Department of Pharmaceutical Analysis, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar 160 062, Punjab, India.
authors.forename: Archana
authors.initials: A
authors.lastname: Sahu
authors.affiliation: Department of Pharmaceutical Analysis, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar 160 062, Punjab, India. Electronic address: ssingh@niper.ac.in.
authors.forename: Saranjit
authors.initials: S
authors.lastname: Singh
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D017315:Cilazapril / Q000031:analogs & derivatives* / Q000737:chemistry; D004355:Drug Stability; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D013058:Mass Spectrometry / Q000379:methods; D010084:Oxidation-Reduction
chemical_list: D017315:Cilazapril; C045980:cilazaprilat
keywords: Cilazapril; Degradation products; LC–MS/TOF and MS(n); LC–NMR and NMR; Stress studies