Isolation and Structure Characterization of Two Novel Degradation Products in Flupirtine Maleate Formulation by Prep-HPLC, LC–MS/Q-TOF and 2D-NMR

摘要: Flupirtine is well accepted as a centrally acting non-opioid analgesic with favorable tolerability. During the stability study of flupirtine maleate drug product, an unknown degradation product (referred to DP-I) exceeding identification threshold was detected by gradient reverse phase HPLC method. To obtain this impurity, subjected stress enhance level DP-I. Furthermore, DP-I and three other thermal degradants DP-II, DP-III DP-IV respectively) were isolated preparative HPLC. An isocratic method developed Welch Xtimate C18 column (250 mm × 30 mm, 5 µm) mobile composed acetonitrile 0.25 % ammonium hydroxide in water 70:30 (v/v). The flow rate 20.0 mL min−1 chromatographic experiments conducted at room temperature. UV detection carried out 252 nm. Based on 1D-NMR, 2D-NMR LC–MS spectral data, structures two novel products confirmed diethyl 5-((4-fluorobenzyl)amino)-2-oxo-1H-imidazo[4,5-b]pyridine-1,3(2H)-dicarboxylate for ethyl (2-(3,4-dimethyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)-6-((4-fluorobenzyl)amino)pyridin-3-yl)carbamate DP-II. Moreover, mechanism from DP-II also proposed.