Spectral evidence for the formation of quinone methide intermediates from 5- and 7-hydroxyflavonoids

Attwood, Michael R.; Brown, B. R.; Lisseter, Stephen G.; Torrero, Christopher L.; Weaver, Philip M.

doi:10.1039/c39840000177

Cited by 21 publications

(7 citation statements)

References 1 publication

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“…Under acidic conditions, such as wine (pH ∼ 3.5), these bonds will cleave, forming an intermediate that is readily attacked by a nucleophile in an S n 1 reaction. 3,4 Historically, the cleavage of the IFL in the presence of an excess nucleophile, as well as subsequent analysis of reaction products, has been used to approximate the degree of polymerization (mDP) and subunit composition of CT material. 5−11 Just as CT extension units have an electrophilic center at C-4 following cleavage, anthocyanins also can act as electrophiles.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Although CT has been shown to also have 4β → 6 branching linkages (Procyanidin B7), previous kinetics work has shown that the cleavage of this type of linkage has a higher activation energy than that of the 4β → 8 linkage. Under acidic conditions, such as wine (pH ∼ 3.5), these bonds will cleave, forming an intermediate that is readily attacked by a nucleophile in an S n 1 reaction. , Historically, the cleavage of the IFL in the presence of an excess nucleophile, as well as subsequent analysis of reaction products, has been used to approximate the degree of polymerization (mDP) and subunit composition of CT material. − …”

Section: Introductionmentioning

confidence: 99%

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Anthocyanin Addition Alters Tannin Extraction from Grape Skins in Model Solutions via Chemical Reactions

Campbell

Grosnickel

Kennedy

et al. 2021

J. Agric. Food Chem.

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Condensed tannin extraction and stable color formation are two of the cornerstones of red wine production. Without condensed tannin, red wine would lack the tactile feeling of astringency, and without the formation of modified pigments, it would lack color stability for long-term aging. To understand how malvidin-3,5-diglucoside interacts with condensed tannin under nonoxidative conditions, an experiment was designed conducting model-wine skin extractions of Sauvignon blanc grapes harvested at various dates of maturity. Monomeric malvidin-3,5-diglucoside was isolated from color concentrate and added during these extractions. Following a 72 h extraction, solutions were evaluated for recovery of monomeric anthocyanins, skin tannin concentration, skin tannin extractability, and impact of anthocyanins on condensed tannin size. Anthocyanins showed a significant impact on the extraction of flavan-3-ol material in the early stages of ripening that declined in the latter stages of ripening. Furthermore, anthocyanins significantly decreased the size of the condensed tannin extracted. These results suggest that anthocyanins are not only enhancing the extractability of condensed tannin but also readily incorporating into the polymeric material, leading to a decrease in the average molecular mass of the condensed tannin polymer. The extent of reaction in 72 h suggests that the rate of interflavan bond cleavage may be higher than previously reported and merits closer scrutiny.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Anthocyanin Addition Alters Tannin Extraction from Grape Skins in Model Solutions via Chemical Reactions

Campbell

Grosnickel

Kennedy

et al. 2021

J. Agric. Food Chem.

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“…25 Richard W. believed that procyanidins could be readily synthesized from flavan-3,4-diols by acid-catalyzed or mild base-catalyzed generation of quinone methide intermediates. 26,27 In addition, different members of the same protein family have different functions. In Fuchsia hybrida, FhDFR3 performed more important roles in the biosynthesis of PAs; FhDFR1 and FhDFR2 were mainly involved in determining the components of the anthocyanins.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Analysis of Metabolic Fluxes from Leucoanthocyanins to Anthocyanins and Proanthocyanidins (PAs)

Wang

Zhang

Жао

et al. 2020

J. Agric. Food Chem.

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Anthocyanins and PAs are the two most common flavonoids, which are widely present among diverse species. Great progress has been made in their synthesis and regulation. In this study, we analyzed the metabolic fluxes from their synthetic precursor leucoanthocyanins, which were obtained by overexpression of dihydroflavonol 4-reductase (DFR) in vitro and in vivo. The unstable product leucocyanidin generated in the CsDFRa enzymatic reaction was easily converted into C-type carbocations under weak acidic conditions, which could be further involved in the synthesis of C-type PAs in vitro. Additionally, the metabolites in tobacco overexpressing CsDFRa and Arabidopsis thaliana DFR and anthocyanidin synthase (ANS) mutants were investigated. In CsDFRa transgenic tobacco, the content of anthocyanins in the petals was greatly increased, but no catechin or PA was detected. In A. thaliana, EC-type carbocation was mainly accumulated in the wild type (WT), and the C-type carbocation was only detected in the ans mutant. In tea plant, the accumulation of C-type PAs is strong positively correlated with the expression of CsDFRa. In summary, leucocyanidin is not only involved in the synthesis of downstream anthocyanin and epicatechin but also can be converted into C-type carbocation to participate in the synthesis of C-type PAs. Hence, from leucocyanidin, three metabolic fluxes were formed toward catechin, cyanidin, and C-type carbocation. These results enriched the metabolic fluxes of leucoanthocyanins and further elaborated the roles of DFR in the process of C-type PA formation.

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“…Figure l suggests that depolymerization stops or slows considerabiy at some point between 12 and 24 h under the reaction conditions used here. Since Attwood et al (1984) have shown that flavanoid quinone methide intermediates exist undef acidic äs well äs basic conditions, the formation of 6 from 2 is also consistent with this mechanism, proceeding through intermediates (11) and (12). The molecular weight of the remaining polymeric material could not be obtained from GPC analyses because of the lack of adequate calibration Standards and knowledge of the structures of these materials.…”

Section: Resultsmentioning

confidence: 55%

Sulfonation of Procyanidin Polymers: Evidence of Intramolecular Rearrangement and Aromatic Ring Substitution

Bae¹,

Malan²,

Karchesy³

1994

HFSG

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The reaction of Douglas-fir polymeric procyanidins with aqueous sodium hydrogen sulfite was investigated by gel permeation chromatography (GPC) and the Isolation and Identification of sulfonated derivatives. GPC profiles of molecular weight over time indicated that epicatechin-(4ß)-sulfonate was rapidly formed initially but did not significantly increase over longer reaction time. Undefined oligomeric materials remained in the reaction mixture, which suggests that other reactions compete with simple acid-catalyzed cleavage of the interflavanoid bond and subsequent formation of 4-substituted flavanoid sulfonates. The Isolation of disodium epicatechin-(4,5')-disulfonate and a functionalized chromene derivative gave evidence that aromatic ring Sulfonation and flavanoid C-ring isomerization are t wo such reactions.'Paper 2898 of the Forest Research Laboratory, Oregon State University, Corvallis, OR 97331, U. S. A. Polymeric procyanidinsDouglas-fir (Pseudotsuga menzesii) inner bark was stripped from a freshly fallen tree, cut into Strips, and iinmersed in methanol.Holzforschung / Vol. 48 / 1994 / No. 2

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Spectral evidence for the formation of quinone methide intermediates from 5- and 7-hydroxyflavonoids

Cited by 21 publications

References 1 publication

Anthocyanin Addition Alters Tannin Extraction from Grape Skins in Model Solutions via Chemical Reactions

Anthocyanin Addition Alters Tannin Extraction from Grape Skins in Model Solutions via Chemical Reactions

Comprehensive Analysis of Metabolic Fluxes from Leucoanthocyanins to Anthocyanins and Proanthocyanidins (PAs)

Sulfonation of Procyanidin Polymers: Evidence of Intramolecular Rearrangement and Aromatic Ring Substitution

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