Online H/D exchange liquid chromatography as a support for the mass spectrometric identification of the oxidation products of melatonin.
The hydrogen-deuterium exchange of protonated melatonin and its in vitro oxidation end-products have been examined by liquid chromatography coupled with ion-trap mass spectrometry. Specific H/D scrambling of protons in the C2 and C4 positions of the indole ring during gas-phase fragmentation process was observed for both melatonin and its oxidation products. Collision-induced dissociation spectra showed losses of variably deuterated NH(3), H(2)O and CH(3)CONH(2). In addition, a similar H/D scrambling behaviour was observed for the oxidation products, obtained from the opening of the indole ring by oxidative attack. Fragmentation pathways are proposed and H/D scrambling has been employed as a fingerprint, allowing identification of N(1)-acetyl-5-methoxykynurenin (AMK), N(1)-acetyl-N(2)-formyl-5-methoxykynurenin (AFMK), dehydro-AFMK and hydroxymelatonin as the oxidation products of melatonin in vitro.
Collin
Fabrice
F
Laboratoire de Chimie-Physique, CNRS UMR 8601, Université Paris Descartes, 45 rue des Saints-Pères, 75006 Paris, France. fabrice.collin@univ-paris5.fr
Bonnefont-Rousselot
Dominique
D
Yous
Saï
S
Marchetti
Catherine
C
Jore
Daniel
D
Gardès-Albert
Monique
M
D002851:Chromatography, High Pressure Liquid; D041961:Deuterium Exchange Measurement; D007735:Kynuramine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D013058:Mass Spectrometry; D008550:Melatonin / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000737:chemistry / Q000378:metabolism
D017382:Reactive Oxygen Species; D007735:Kynuramine; C041550:N-acetyl-N-formyl-5-methoxykynurenamine; C032131:N-acetyl-5-methoxy kynurenamine; D008550:Melatonin