Mechanism of quercetin oxygenation a possible model for haem degradation
作者:V. Rajananda、Stanley B. Brown
DOI:10.1016/s0040-4039(01)82948-8
日期:1981.1
Quercetin undergoes base-catalysed oxidative decarbonylation by a mechanism involving only one oxygen molecule, unlike the apparently similar step in haem catabolism, which requires two oxygen molecules.
Flavonoid Oxidation by the Radical Generator AIBN: A Unified Mechanism for Quercetin Radical Scavenging
作者:Venkat Krishnamachari、Lanfang H. Levine、Paul W. Paré
DOI:10.1021/jf020045e
日期:2002.7.1
nucleophiles revealed that two of the products, namely the substituted benzofuranone (2) and the depside (4), are generated from a common carbocationintermediate. Indirect evidence for the operation of a cyclic concerted mechanism in the formation of the dimeric product (3) is provided. The identification of these products supports the model that the principal site of scavenging reactive oxygen species (ROS)
In order to clarify the mechanism for the radical-capturing reaction which is initiated at the C3-hydroxyl group of flavonols, 5,7,3',4'-tetramethylquercetin (TMQ) was reacted with the 2,2'-azobis-isobutyronitrile (AIBN) radical initiator in benzene. Six products, one depside and its two hydrolytic products, one nitrile adduct, and two others, were isolated from tne reaction mixture, and their structures were determined by instrumental analyses. The quantitative change to the four main products against the reaction time was measured by an HPLC method. The radical-capturing reaction pathway for TMQ with AIBN is proposed from these products and their quantitative changes. The pathway dividing into two clearly reveals that one sub-path formed the depside and its hydrolytic products, while the other formed the nitrile adduct. The reactivity of each two sub-path was nearly the same, different from the case of TMQ and the 2,2'-azobis-2,4-dimethylvaleronitrile (AMVN) radical initiator.