title: Electrochemical oxidation of berberine and mass spectrometric identification of its oxidation products.
abstract: Electrochemical oxidation of the isoquinoline alkaloid berberine in aqueous medium was studied by cyclic and differential pulse voltammetry at a glassy carbon electrode (GCE). Two anodic peaks of the quaternary form of berberine were observed at +1.2V and +1.4V (vs. SCE) in acidic and neutral solutions. When the anodic polarization exceeded the value of +1.1 V, the redox active film is formed on the GCE surface. The formation of adsorbed film was well-documented by quasireversible redox couple at +0.25 V which was studied in redox cycling experiments. In alkaline medium, a new anodic peak at +0.5 V appeared due to oxidation of berberine pseudobase to 8-oxoberberine. Solutions of berberine at different pH were subjected to controlled potential electrolysis on platinum gauze electrode and analyzed using liquid chromatography (HPLC) equipped with electrospray ionization/quadrupole time-of-flight mass spectrometry. The main water soluble monomeric product of berberine oxidation under physiological-near experimental conditions, OP1, was identified as demethyleneberberine cation (2,3-dihydroxy-9,10-dimethoxy-5,6-dihydroisoquinolino[3,2-a]isoquinolin-7-ium).
authors.affiliation: Department of Analytical Chemistry, Faculty of Science, Palacký University, Olomouc, Czech Republic.
authors.forename: Jana
authors.initials: J
authors.lastname: Skopalová
authors.forename: Jan
authors.initials: J
authors.lastname: Vacek
authors.forename: Barbora
authors.initials: B
authors.lastname: Papoušková
authors.forename: David
authors.initials: D
authors.lastname: Jirovský
authors.forename: Vítězslav
authors.initials: V
authors.lastname: Maier
authors.forename: Václav
authors.initials: V
authors.lastname: Ranc
mesh_terms: D001599:Berberine / Q000031:analogs & derivatives* / Q000737:chemistry; D002244:Carbon; D002851:Chromatography, High Pressure Liquid; D055664:Electrochemical Techniques; D004566:Electrodes; D004583:Electrons; D005898:Glass; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010984:Platinum; D021241:Spectrometry, Mass, Electrospray Ionization; D014867:Water
chemical_list: D014867:Water; D001599:Berberine; D010984:Platinum; C103789:8-oxoberberine; D002244:Carbon