title: Photooxidation of alkaloids: considerable quantum yield enhancement by rose bengal-sensitized singlet molecular oxygen generation.
abstract: The photooxidation of sanguinarine, coralyne and berberine was studied in oxygenated alkaline methanol solutions. Rose bengal as photosensitizer significantly accelerates the process, indicating the importance of singlet molecular oxygen in the reaction mechanism. The quantum yield of sensitized oxidation was found to increase significantly with pH and reaches 0.4 for berberine at pH 13.8. The direct oxidation of alkaloids is less efficient, the quantum yield does not exceed 0.01 even in oxygen-saturated solutions. The photoinduced electron ejection does not play a role in the oxidation. The uncharged pseudobase forms, which are present in alkaline medium, are oxidized much more easily than the alkaloid cations.
authors: Max-Planck-Institut für Bioanorganische Chemie, Mülheim an der Ruhr, Germany.
authors: Helmut
authors: H
authors: Görner
authors: Zsombor
authors: Z
authors: Miskolczy
authors: Mónika
authors: M
authors: Megyesi
authors: László
authors: L
authors: Biczók
mesh_terms: D000470:Alkaloids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010777:Photochemistry; D011789:Quantum Theory; D012395:Rose Bengal / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*
chemical_list: D000470:Alkaloids; D026082:Singlet Oxygen; D012395:Rose Bengal