Peroxidase-Catalyzed Formation of Quercetin Quinone Methide–Glutathione Adducts

The oxidation of quercetin by horseradish peroxidase/H2O2 was studied in the absence but especially also in the presence of glutathione (GSH). HPLC analysis of the reaction products formed in the absence of GSH revealed formation of at least 20 different products, a result in line with other studies...

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Bibliographic Details
Published in:Archives of biochemistry and biophysics 2000-06, Vol.378 (2), p.224-233
Main Authors: Awad, Hanem M., Boersma, Marelle G., Vervoort, Jacques, Rietjens, Ivonne M.C.M.
Format: Article
Language:English
Subjects:
Biochemie
Biochemistry
Chromatography, High Pressure Liquid
Electrons
Flavonoids - chemistry
Flavonoids - metabolism
Glutathione - metabolism
glutathione adducts
Horseradish Peroxidase - metabolism
Hydrogen Peroxide - metabolism
Leerstoelgroep Toxicologie
Magnetic Resonance Spectroscopy
o-quinone
oxidation
p-quinone methide
quercetin
Quercetin - analogs & derivatives
Quercetin - chemistry
Quercetin - metabolism
semiquinone
Sub-department of Toxicology
Time Factors
Toxicologie
Toxicology
VLAG
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Summary:The oxidation of quercetin by horseradish peroxidase/H2O2 was studied in the absence but especially also in the presence of glutathione (GSH). HPLC analysis of the reaction products formed in the absence of GSH revealed formation of at least 20 different products, a result in line with other studies reporting the peroxidase-mediated oxidation of flavonoids. In the presence of GSH, however, these products were no longer observed and formation of two major new products was detected. 1H NMR identified these two products as 6-glutathionylquercetin and 8-glutathionylquercetin, representing glutathione adducts originating from glutathione conjugation at the A ring instead of at the B ring of quercetin. Glutathione addition at positions 6 and 8 of the A ring can best be explained by taking into consideration a further oxidation of the quercetin semiquinone, initially formed by the HRP-mediated one-electron oxidation, to give the o-quinone, followed by the isomerization of the o-quinone to its p-quinone methide isomer. All together, the results of the present study provide evidence for a reaction chemistry of quercetin semiquinones with horseradish peroxidase/H2O2 and GSH ultimately leading to adduct formation instead of to preferential GSH-mediated chemical reduction to regenerate the parent flavonoid.
ISSN:0003-9861
1096-0384
DOI:10.1006/abbi.2000.1832