Rapid Reversed Phase Ultra-Performance Liquid Chromatography Analysis of the Major Cocoa Polyphenols and Inter-relationships of Their Concentrations in Chocolate

Karen A. Cooper,† Esther Campos-Giménez,† Diego Jiménez Alvarez,† Kornél Nagy,† Jennifer L. Donovan,§ and Gary Williamson*†
Nestl Research Center, CH-1000 Lausanne 26, Switzerland, and Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, South Carolina 29425
J. Agric. Food Chem., 2007, 55 (8), pp 2841–2847
DOI: 10.1021/jf063277c
Publication Date (Web): March 16, 2007
Copyright © 2007 American Chemical Society
†

 Nestlé Research Center.

,
§

 Medical University of South Carolina.

,
*

 Address correspondence to this author at the Nestle Research Center, Vers-Chez-les-Blanc, 1000 Lausanne, Switzerland (e-mail gary.williamson@ rdls.nestle.com; telephone +41 21 785 8546; fax +41 21 785 8544).

Abstract

Chocolate and other cocoa-containing products are a rich source of polyphenols. This paper describes an ultra-performance liquid chromatography (UPLC) method that can separate and quantify in 3 min six of the major chocolate polyphenols:  catechin; epicatechin; B2 (epicatechin-4β-8-epicatechin); B5 (epicatechin-4β-6-epicatechin); C1 (epicatechin-4β-8-epicatechin-4β-8-epicatechin); and tetramer D (epicatechin-4β-8-epicatechin-4β-8-epicatechin-4β-8-epicatechin). A survey of 68 chocolate samples indicated that there was a strongly predictive relationship between epicatechin and the other individual polyphenols, especially procyanidin B2 (R 2 = 0.989), even though the chocolates came from varied sources and manufacturers. The relationship was less strong with catechin, and so further work to explore the reasons for this difference was performed. Chiral analysis on a subset of 23 chocolates showed that (−)-epicatechin had a predictive relationship with (+)-catechin in line with the other polyphenols, but not with (−)-catechin (the predominant form). This indicates that (−)-catechin is the most affected by manufacturing conditions, possibly formed through epimerization from (−)-epicatechin during processing. The results show that epicatechin concentrations can be used to predict the content of other polyphenols, especially B2 and C1, and total polyphenols content. Finally, the (−)-catechin content is not predictable from the epicatechin content, and it is concluded that this is the main form of polyphenol that varies according to manufacturing conditions and cocoa origin.

Keywords: Chocolate; UPLC; procyanidins; epicatechin; antioxidant; cocoa; polyphenols

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History

  • Published In Issue April 18, 2007
  • Received for review November 13, 2006. Revised manuscript received January 31, 2007. Accepted February 4, 2007. Funded by Nestlé Research Center.

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