Study of the reaction products of flavonols with 2,2-diphenyl-1-picrylhydrazyl using liquid chromatography coupled with negative electrospray ionization tandem mass spectrometry

✍ Scribed by Erlend Hvattum; Yngve Stenstrøm; Dag Ekeberg

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 415 KB
• Volume: 39
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.756

✦ Synopsis

The products obtained after the reaction between flavonols and the stable free radical 2,2-diphenyl-1picrylhydrazyl (DPPH ž ) in both methanol and acetonitrile were characterized using liquid chromatography

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 ž 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)-3,5,7trihydroxy-2,3-dimethoxy-2,3-dihydrochromen-4-one and 2-(3,4-dihydroxyphenyl)-3,3,5,7-tetrahydroxy-2methoxy-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 ž , reacted with CH 3 OH through the addition of CH 3 O ž , 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 ž . In contrast, kaempferol formed two isomeric products where a kaempferol radical reacted with H 2 O through the addition of OH ž , i.e. similar to the reaction of kaempferol radicals with CH 3 OH.