Activité anti-oxydante de flavonoïdes réactivitë avec le superoxyde de potassium en phase hétérogène

Tournaire, Cécile; Hocquaux, M.; Beck, I.; Oliveros, Esther; Maurette, Marie-Thérèse

doi:10.1016/s0040-4020(01)85507-1

Cited by 25 publications

(15 citation statements)

References 21 publications

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“…The mass spectral data for 4 and its methoxyl derivative were consistent and confirmed the structural assignments. This phenolic carboxylic acid ester, a depside, has been reported under different oxidation conditions such as singlet oxygen and superoxide anion radical (13,14), as well as in the enzyme system using quercetinase (15). However, the absence of 13 C NMR data in the earlier reports has raised doubts as to its correct identification (6).…”

Section: Resultsmentioning

confidence: 99%

“…The formation of depsides and substituted 3(2H)benzofuranones have been reported in several oxidation systems (6,7,13,14). Electrochemical oxidation of quercetin and kaempferol is thought to proceed through a two-electron oxidation, first to yield a 3,4-flavandione (10) which rearranges to form a substituted 3(2H)benzofuranone through the chalcan-trione ringchain tautomer (11, Scheme 1) (6,7).…”

Section: Resultsmentioning

confidence: 99%

“…Investigations with a superoxide anion radical mediated oxidation of quercetin (Scheme 2) is thought to generate a C-2 centered anion (12) followed by a cyclic peroxide (13) rearranging to the depside product (13,14). Using AMVN and AIBN as radical initiators and tetramethylquercetin (14) as substrate, the depside observed (16) has been proposed to be generated via a C-2 centered radical (15, Scheme 3).…”

Section: Resultsmentioning

confidence: 99%

“…Using AMVN and AIBN as radical initiators and tetramethylquercetin (14) as substrate, the depside observed (16) has been proposed to be generated via a C-2 centered radical (15, Scheme 3). However, direct evidence for this mechanism was not provided (23,24).…”

Section: Resultsmentioning

confidence: 99%

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Flavonoid Oxidation by the Radical Generator AIBN: A Unified Mechanism for Quercetin Radical Scavenging

Krishnamachari

Levine

Paré

2002

J. Agric. Food Chem.

144

120

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Four oxidized flavonoid derivatives generated from reacting quercetin (a pentahydroxylated flavone) with the peroxyl radical generator 2,2'-azobis-isobutyronitrile (AIBN) were isolated by chromatographic methods and identified by NMR and MS analyses. Compounds included 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (2); 1,3,11a-trihydroxy-9-(3,5,7-trihydroxy-4H-1-benzopyran-4-on-2-yl)-5a-(3,4-dihydroxyphenyl)-5,6,11-hexahydro-5,6,11-trioxanaphthacene-12-one (3); 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoic acid (4); and methyl 3,4-dihydroxyphenylglyoxylate (5). Product ratios under different hydrogen ion concentrations and external nucleophiles revealed that two of the products, namely the substituted benzofuranone (2) and the depside (4), are generated from a common carbocation intermediate. 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 quercetin is the o-dihydroxyl substituent in the B-ring, as well as the C-ring olefinic linkage.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Flavonoid Oxidation by the Radical Generator AIBN: A Unified Mechanism for Quercetin Radical Scavenging

Krishnamachari

Levine

Paré

2002

J. Agric. Food Chem.

144

120

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“…Acetonitrile and methanol were HPLC grade, and other chemicals were reagent grade. 3-Methoxyquercetin (1), 3,4′-dihydroxyflavone (5), 3,3′,4′-trihydroxyflavone (6), and 3,3′-dihydroxy-4′-methoxyflavone (7) were synthesized in our laboratory. Diazomethane was generated from diazald (N-methyl-N-nitroso-ptoluenesulfonamide, Aldrich Chemical Co.) following standard procedures.…”

Section: Methodsmentioning

confidence: 99%

In Vitro Flavon-3-ol Oxidation Mediated by a B Ring Hydroxylation Pattern

Krishnamachari

Levine

Zhou

et al. 2004

Chem. Res. Toxicol.

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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.

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Polyphenols produced during red wine ageing

1997

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Over the past few years, it has been accepted that a moderate red wine consumption is a factor beneficial to human health. Indeed, people of France and Italy, the two major wine-producing European countries, eat a lot of fatty foods but suffer less from fatal heart strokes than people in North-America or in the northern regions of Europe, where wine is not consumed on a regular basis. For a time, ethanol was thought to be the "good" chemical species hiding behind what is known as the "French paradox". Researchers now have turned their investigations towards a family of natural substances called "polyphenols", which are only found in plants and are abundant in grapes. It is well known that these molecules behave as radical scavengers and antioxidants, and it has been demonstrated that they can protect cholesterol in the LDL species from oxidation, a process thought to be at the origin of many fatal heart attacks. However, taken one by one, it remains difficult to demonstrate which are the best polyphenols as far as their antioxidant activities are concerned. The main obstacle in that kind of research is not the design of the chemical and biological tests themselves, but surprisingly enough, the limited access to chemically pure and structurally elucidated polyphenolic compounds. In this article, particular attention will be paid to polyphenols of red wine made from Vitis vinifera cultivars. With respect to the "French paradox", we address the following question: are wine polyphenolic compounds identical to those found in grapes (skin, pulp and seed), or are there biochemical modifications specifically taking place on the native flavonoids when a wine ages? Indeed, structural changes occur during wine conservation, and one of the most studied of those changes concerns red wine colour evolution, called "wine ageing". As a wine ages, it has been demonstrated that the initially present grape pigments slowly turn into new more stable red pigments. That phenomenon goes on for weeks, months and years. Since grape and wine polyphenols are chemically distinct, their antioxidant activities cannot be the same. So, eating grapes might well lead to beneficial effects on human health, due to the variety and sometimes large amounts of their polyphenolic content. However, epidemiological surveys have focused on wines, not on grapes....

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Activité anti-oxydante de flavonoïdes réactivitë avec le superoxyde de potassium en phase hétérogène

Cited by 25 publications

References 21 publications

Flavonoid Oxidation by the Radical Generator AIBN: A Unified Mechanism for Quercetin Radical Scavenging

Flavonoid Oxidation by the Radical Generator AIBN: A Unified Mechanism for Quercetin Radical Scavenging

In Vitro Flavon-3-ol Oxidation Mediated by a B Ring Hydroxylation Pattern

Polyphenols produced during red wine ageing

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