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(-)-Catechin in Cocoa and Chocolate: Occurence and Analysis of an Atypical Flavan-3-ol Enantiomer
University of Bonn, Department of Nutrition and Food Sciences, Research Area: Food Chemistry I, Endenicher Allee 11-13, 53115 Bonn, Germany
* Author to whom correspondence should be addressed.
Received: 30 May 2007; in revised form: 2 July 2007 / Accepted: 2 July 2007 / Published: 4 July 2007
Abstract: 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-phase-extraction and LC-MS analysis. As expected, we found (-)-epicatechin and (+)-catechin inunfermented, 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.
Keywords: Flavonoids; Cocoa; Chocolate; Catechin; Epicatechin; Epimerization; Enantioseparation; Capillary Electrophoresis; LC-MS; Isolation; Purification
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Kofink, M.; Papagiannopoulos, M.; Galensa, R. (-)-Catechin in Cocoa and Chocolate: Occurence and Analysis of an Atypical Flavan-3-ol Enantiomer. Molecules 2007, 12, 1274-1288.
Kofink M, Papagiannopoulos M, Galensa R. (-)-Catechin in Cocoa and Chocolate: Occurence and Analysis of an Atypical Flavan-3-ol Enantiomer. Molecules. 2007; 12(7):1274-1288.
Kofink, Michael; Papagiannopoulos, Menelaos; Galensa, Rudolf. 2007. "(-)-Catechin in Cocoa and Chocolate: Occurence and Analysis of an Atypical Flavan-3-ol Enantiomer." Molecules 12, no. 7: 1274-1288.