Senecionine n oxide

Lasiocarpine (Las) and lasiocarpine N-oxide were ordered from Cfm Oskar Tropitzsch (Marktredwitz, Germany). Lycopsamine (Lyc), Lycopsamine N-oxide, europine (Eur), europine N-oxide, senecionine (Sen), senecionine N-oxide, echimidine (Ech), echimidine N-oxide, intermedine, intermedine N-oxide, jacobine, jacobine N-oxide, heliosupine, heliosupine N-oxide, retrorsine N-oxide, retronecine, and senkirkine were obtained from Phytolab (Vestenbergsgreuth, Germany). Retrorsine (Ret) was delivered by AppliChem (Darmstadt, Germany). Methanol (MeOH, LC–MS grade) and water (H₂O, LC–MS grade) were purchased from Merck KGA (Darmstadt, Germany). 7,9-Diglutathionyl-6,7-dihydro-1-hydroymethyl-5H-pyrrolizidine was obtained from ASCA (Berlin, Germany). Potassium cyanide (KCN), isotopically labeled potassium cyanide (KCX, K¹³C¹⁵N), glutathione and isotopically labeled glutathione (GSX, ¹³C₂¹⁵N-GSH), and all other chemicals and co-factors were purchased from Sigma-Aldrich (Steinheim, Germany). All chemicals were obtained in analytical grade, if available. Human liver microsomes (mixed gender from 50 donors; protein concentration 20 mg/mL; cytochrome P450 content 310 pmol/mg protein) and rat liver microsomes (male Sprague–Dawley rats; protein concentration 20 mg/mL; cytochrome P450 content 700 pmol/mg protein) were obtained from Corning (Corning, USA).

Analytical standards of all pyrrolizidine alkaloids and their N-oxide were purchased from Phytolab (Vestenbergsgreuth, Germany): Echimidine (Em), Echimidine-N-oxide (EmNO), Echinatine (En), Echinatine-N-oxide (EnNO), Erucifoline-N-oxide (ErNO), Europine (Eu), Europine-N-oxide (EuNO), Heliosupine (Hs), Heliosupine-N-oxide (HsNO), Heliotrine (Ht), Heliotrine-N-oxide (HtNO), Indicine (Id), Indicine-N-oxide (IdNO), Integerrimine (Ir), Integerrimine-N-oxide (IrNO), Intermedine (Im), Intermedine-N-oxide (ImNO), Lasiocarpine (Lc), Lycopsamine (Ly), Lycopsamine-N-oxide (LyNO), Retrorsine (Rt), Retrorsine-N-oxide (RtNO), Rinderine (Rn), Rinderine-N-oxide (RnNO), Senecionine (Sn), Senecionine-N-oxide (SnNO), Seneciphylline (Sp), Seneciphylline-N-oxide (SpNO), Senecivernine (Sv), Senecivernine-N-oxide (SvNO), Senkirkine (Sk), Spartioidine (St), Spartioidine-N-oxide (StNO), Usaramine (Us) and Usaramine-N-oxide (UsNO). Methanol (LC-MS grade) was from VWR Chemicals (Rosny-sous-Bois-cedex, France), sulphuric acid (96%) and acetonitrile (LC-MS grade) were from Carlo Erba Reagents (Val de Reuil Cedex, France), formic acid was from Carlo Erba Reagents (Milan, Italy) and ammonium formate (analytical grade) was from Sigma-Aldrich (St. Louis, MO, USA). Ultrapure water used throughout the experiments was produced by an EvoQua Water Technologies system (Diessechem, Milan, Italy).

Methanol (MeOH) (MS grade), acetonitrile (MeCN) (MS grade), formic acid (FA) (MS grade), ammonium formate (MS grade), acetone (HPLC grade), sulfuric acid, hydrochloric acid (Analytical reagent grade) and caffeine (internal standard, for spiking experiments and method validation) were purchased from Sigma-Aldrich (Steinheim, Germany). Glass fibre (SiO₂, particle size 0.2–0.8 mm) was purchased from Merck (Darmstadt, Germany). Certified reference materials of heliotrine, monocrotaline, monocrotaline N-oxide, senecionine, senecionine N-oxide, erucifoline, erucifoline-N-oxide, retrorsine, jacobine, jacobine N-oxide senkirkine, heliotrine N-oxide, echimidine, echimidine N-oxide, purchased from Phytolab (Vestenbergsgreuth, Germany), also lindelofine, lindelofine N-oxide purchased from AKos Consulting & Solutions (Steinen, Germany). Oasis MCX 6 cc, 150 mg Sorbent, 30 μm particle size purchased from Waters (Milford, USA). MilliQ water (resistivity 18.2 Mohm × cm, TOC less than 1 μg L⁻¹) was produced in-house with a type I ultrapure water purification system from ELGA-Veolia LabWater (High Wycombe, UK).