Study of the reaction products of flavonols with 2,2-diphenyl-1-picrylhydrazyl using liquid chromatography coupled with negative electrospray ionization tandem mass spectrometry
作者:Erlend Hvattum、Yngve Stenstrøm、Dag Ekeberg
DOI:10.1002/jms.756
日期:2004.12
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 CH3OH molecules or one CH3OH- and one H2O 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 CH3OH through the addition of CH3O•, 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 H2O through the addition of OH•, i.e. similar to the reaction of kaempferol radicals with CH3OH. Copyright © 2004 John Wiley & Sons, Ltd.
甲醇和
乙腈中
黄酮醇与稳定自由基2,2
-二苯基-1-苦基
肼(
DPPH•)反应所得产物的表征采用负极
液相色谱串联电喷雾电离质谱(LC/ESI-MS/MS)和核磁共振波谱法。被研究的
黄酮醇为
槲皮素、
山柰酚和
杨梅素。用LC/ESI-MS/MS和NMR鉴定了
甲醇中的两种氧化
槲皮素产物。
槲皮素通过两个H原子向
DPPH•转移而被氧化,随后以两种 H分子或一种 H-和一种
H2O分子分别得到产物2-(3,4-二羟基苯基)-3,5,7-三羟基-2,3-二甲氧基-2,3-二氢色烯-4-酮和2-(3,4-二羟基苯基)-3,3,5,7-四羟基-2-甲氧基-2,3-二氢色烯-4-酮。LC/ESI-MS/MS分析表明,在
甲醇中,
山柰酚和
杨梅素也产生了与
槲皮素类似的甲氧基化氧化产物。此外,
山柰酚还显示出了一种
山柰酚自由基通过一个H原子转移到
DPPH•,再通过
CH3O•的加成反应与 H反应,产生了两种异构产物。当反应发生在
乙腈中时,LC/ESI-MS/MS分析显示,
槲皮素和
杨梅素均通过两个H原子向
DPPH•转移而形成了稳定的异构醌产物。相反,
山柰酚形成两种异构产物,其中
山柰酚自由基通过OH•的加入与 反应,即与
山柰酚自由基与 H的反应类似。[13]。