Kinetics of epimerization of (+)-catechin and its rearrangement to catechinic acid

Kiatgrajai, Preecha; Wellons, J. D.; Gollob, Lawrence; White, James D.

doi:10.1021/jo00136a021

Cited by 90 publications

(38 citation statements)

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“…Consequently, in comparison to the (-)-catechin levels, only small amounts of (+)-epicatechin would likely be formed during the epimerization reaction; (2) generally, the sensitivity of the detection used in CCE is limited and moreover the small amounts of (+)-epicatechin are not sufficiently separated from the close eluting predominant (-)-epicatechin peak; (3) the transoid structure of the substituents at C-2 and C-3 in catechin is thermodynamically favoured over the cisoid structure in epicatechin (see Figure 1). The formation of (-)-catechin from (-)-epicatechin is therefore likely favoured in comparison to the formation of (+)-epicatechin from (+)-catechin [31]. These factors might all together account for this finding.…”

Section: Comparison Of the Flavan-3-ol Peak Ratiosmentioning

confidence: 90%

(-)-Catechin in Cocoa and Chocolate: Occurence and Analysis of an Atypical Flavan-3-ol Enantiomer

2007

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Cocoa contains high levels of different flavonoids. In the present study, the enantioseparation of catechin and epicatechin in cocoa and cocoa products by chiral capillary electrophoresis (CCE) was performed. A baseline separation of the catechin and epicatechin enantiomers was achieved by using 0.1 mol·L −1 borate buffer (pH 8.5) with 12 mmol·L -1 (2-hydroxypropyl)-γ-cyclodextrin as chiral selector, a fused-silica capillary with 50 cm effective length (75 μm I.D.), +18 kV applied voltage, a temperature of 20 °C and direct UV detection at 280 nm. To avoid comigration or coelution of other similar substances, the flavan-3-ols were isolated and purified using polyamide-solid-phaseextraction and LC-MS analysis. As expected, we found (-)-epicatechin and (+)-catechin in unfermented, dried, unroasted cocoa beans. In contrast, roasted cocoa beans and cocoa products additionally contained the atypical flavan-3-ol (-)-catechin. This is generally formed during the manufacturing process by an epimerization which converts (-)-epicatechin to its epimer (-)-catechin. High temperatures during the cocoa bean roasting process and particularly the alkalization of the cocoa powder are the main factors inducing the epimerization reaction. In addition to the analysis of cocoa and cocoa products, peak ratios were calculated for a better differentiation of the cocoa products.

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Section: Comparison Of the Flavan-3-ol Peak Ratiosmentioning

confidence: 90%

(-)-Catechin in Cocoa and Chocolate: Occurence and Analysis of an Atypical Flavan-3-ol Enantiomer

2007

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“…With increasing pH an isomerization at the C2 position to yield (2S, 3S)-ent-epicatechin and (2S, 3R)-ent-catechin has been observed, (2R, 3S)-catechin being more stable than the (2R, 3R)-epicatechin [29,30]. The oligomeric procyanidins decompose and isomerize at pH 2.…”

Section: Chemical Propertiesmentioning

confidence: 98%

Analysis of proanthocyanidins

Hümmer

Schreier²

2008

Molecular Nutrition Food Res

211

269

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“…Kiatgrajai et al 5 ) have reported that the epimerization of ( + )-C gave an equilibrium mixture in which (+ )-C predominated over its epimer (( + )-EC), and further that the epimerization of ( -)-EC was 2-3 times more rapid than that of (+ )-C. Thus, those catechins with a 2,3-trans configuration are considered to be stereo chemically more stable than those possessing a 2,3-cis configuration.…”

Section: Epimerization Conditions For the Tea Catechinsmentioning

confidence: 99%