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Study of the reaction products of flavonols with 2,2‐diphenyl‐1‐picrylhydrazyl using liquid chromatography coupled with negative electrospray ionization tandem mass spectrometry
Author(s) -
Hvattum Erlend,
Stenstrøm Yngve,
Ekeberg Dag
Publication year - 2004
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.756
Subject(s) - chemistry , flavonols , kaempferol , myricetin , dpph , electrospray ionization , quercetin , tandem mass spectrometry , chromatography , mass spectrometry , organic chemistry , medicinal chemistry , antioxidant
The products obtained after the reaction between flavonols and the stable free radical 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH • ) in both methanol and acetonitrile were characterized using liquid chromatography coupled with negative electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) and NMR spectroscopy. The flavonols studied were quercetin, kaempferol and myricetin. In methanol, two reaction products of oxidized quercetin were identified using LC/ESI‐MS/MS and NMR. Quercetin was oxidized through a transfer of two H‐atoms to DPPH • and subsequently incorporated either two CH 3 OH molecules or one CH 3 OH‐ and one H 2 O molecule giving the products 2‐(3,4‐dihydroxyphenyl)‐3,5,7‐trihydroxy‐2,3‐dimethoxy‐2,3‐dihydrochromen‐4‐one and 2‐(3,4‐dihydroxyphenyl)‐3,3,5,7‐tetrahydroxy‐2‐methoxy‐2,3‐dihydrochromen‐4‐one, respectively. LC/ESI‐MS/MS analysis revealed that in methanol, kaempferol and myricetin also gave rise to methoxylated oxidation products similar to that identified for quercetin. Kaempferol, in addition, also exhibited products where a kaempferol radical, obtained by a transfer of one H‐atom to DPPH • , reacted with CH 3 OH through the addition of CH 3 O • , yielding two isomeric products. When the reaction took place in acetonitrile, LC/ESI‐MS/MS analysis showed that both quercetin and myricetin formed stable isomeric quinone products obtained by a transfer of two H‐atoms to DPPH • . In contrast, kaempferol formed two isomeric products where a kaempferol radical reacted with H 2 O through the addition of OH • , i.e. similar to the reaction of kaempferol radicals with CH 3 OH. Copyright © 2004 John Wiley & Sons, Ltd.