TY - JOUR
T1 - In vitro flavon-3-ol oxidation mediated by a B ring hydroxylation pattern
AU - Krishnamachari, Venkat
AU - Levine, Lanfang H.
AU - Zhou, Chun
AU - Paré, Paul W.
N1 - Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2004/6
Y1 - 2004/6
N2 - Flavonols are potent naturally occurring antioxidants. Chemical oxidation reactions in combination with modern spectroscopic techniques have been employed to identify oxidized flavonoid products. Although many oxidized derivatives have been generated from commercially available starting materials, few studies have developed a sequence of flavonoid substrates with a particular hydroxylation pattern to probe the mechanism of flavonoid oxidation. Here, we use AIBN (2,2′-azobisisobutyronitrile) in combination with a series of hydroxylated flavonols to probe the mechanism of flavonoid dimer formation and the role of singly or doubly oxidized species in generating and promoting oxidized flavonoid products. 3-Methoxyquercetin (3-hydroxyl group blocked) and luteolin (lack of 3-hydroxyl) were reacted with AIBN alone or with a second flavonol to serve as a C-3 hydroxyl donor to examine the mechanism of dimer formation. 3-Hydroxyflavones with increasing hydroxyl substitutions in the B ring were also reacted with AIBN in the presence or absence of an external nucleophile to examine the role of various hydroxyls in the formation of a carbocation intermediate via a doubly oxidized species. The presence of a free C-3 hydroxyl, coupled with a B ring ortho hydroxy unit, appears essential for dimer formation. An increase in the number of hydroxyls in the B ring facilitates products generated from a doubly oxidized species.
AB - Flavonols are potent naturally occurring antioxidants. Chemical oxidation reactions in combination with modern spectroscopic techniques have been employed to identify oxidized flavonoid products. Although many oxidized derivatives have been generated from commercially available starting materials, few studies have developed a sequence of flavonoid substrates with a particular hydroxylation pattern to probe the mechanism of flavonoid oxidation. Here, we use AIBN (2,2′-azobisisobutyronitrile) in combination with a series of hydroxylated flavonols to probe the mechanism of flavonoid dimer formation and the role of singly or doubly oxidized species in generating and promoting oxidized flavonoid products. 3-Methoxyquercetin (3-hydroxyl group blocked) and luteolin (lack of 3-hydroxyl) were reacted with AIBN alone or with a second flavonol to serve as a C-3 hydroxyl donor to examine the mechanism of dimer formation. 3-Hydroxyflavones with increasing hydroxyl substitutions in the B ring were also reacted with AIBN in the presence or absence of an external nucleophile to examine the role of various hydroxyls in the formation of a carbocation intermediate via a doubly oxidized species. The presence of a free C-3 hydroxyl, coupled with a B ring ortho hydroxy unit, appears essential for dimer formation. An increase in the number of hydroxyls in the B ring facilitates products generated from a doubly oxidized species.
UR - http://www.scopus.com/inward/record.url?scp=3042842883&partnerID=8YFLogxK
U2 - 10.1021/tx034242z
DO - 10.1021/tx034242z
M3 - Article
C2 - 15206900
AN - SCOPUS:3042842883
VL - 17
SP - 795
EP - 804
JO - Chemical Research in Toxicology
JF - Chemical Research in Toxicology
SN - 0893-228X
IS - 6
ER -