Isolation and characterization of novel degradation products in fenoverine by LC-QTOF-MS/MS, LC-MSn and 2D-NMR

Abstract

This study investigates the degradation profile of fenoverine (FEN), an antispasmodic drug, following the International Conference on Harmonization (ICH) Q1A (R2) guidelines. FEN is stable in the presence of light, humidity, and thermal stress; however, it is highly susceptible to oxidative stress (0.1% H₂O₂) and alkaline stress (0.1 N NaOH), and has low susceptibility to acid (1 N HCl). Seven degradation products (DPs) were identified using a mass-compatible ultra-high-performance liquid chromatography (UPLC) method: five oxidative degradation products (FOD1 to FOD5) and two alkaline degradation products (FAD1 and FAD2). All DPs, except for FOD4, were isolated through preparative HPLC and structurally characterized using high-resolution mass fragmentation, multistage fragmentation, and multidimensional nuclear magnetic resonance (NMR) spectroscopy. Notably, FOD3, FOD4, and FOD5 were identified as isomeric oxidative degradation products (M + 16 Da). Atmospheric pressure chemical ionization (APCI) mass spectrometry and NMR studies pinpointed the oxidation sites, distinguishing FOD3 as FEN's N-oxide, FOD4 as its hydroxyl product, and FOD5 as the sulfoxide. To the best of our knowledge, the discussion of FOD1 to FOD5 and FAD1 in the context of this study appears to be unique and not documented in prior literature. These degradation products were successfully separated from FEN using an Acquity UPLC BEH300 C18 column with 1.7 μm particles as the stationary phase and a mobile phase of 10 mM ammonium acetate in water (pH adjusted to 9.0), with acetonitrile and methanol (80 : 20, v/v) as co-solvents. In silico toxicity predictions were conducted, which revealed no structural alerts indicative of mutagenicity for any of the seven degradation products (FOD1 to FOD5, FAD1, and FAD2).