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Articles

More Antioxidants in Cocoa

¹ Physical Chemistry-PRALIB, School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina

John F. Hammerstone², Sheryl A. Lazarus² and Harold Schmitz²

² Analytical and Applied Sciences Group, Mars Incorporated, Hackettstown, NJ 07840

Carl L. Keen³

³ Department of Nutrition University of California, Davis Davis, CA 95616

	INTRODUCTION

TOP INTRODUCTION REFERENCES

 
Dear Dr. Lamuela-Raventos:

The letter by Lamuela-Raventos et al. discussed data that suggest quercetin could be contributing to a significant part of the antioxidant activity observed in humans after the consumption of chocolate. We agree that it is a point worth discussing for two aspects: a) a comparison of the levels of quercetin and catechins/oligomers (procyanidins) found in chocolate and b) whether the levels are sufficient to exert an antioxidant effect after consumption.

First, when attempting to elucidate the active compounds responsible for the antioxidant action of a food, it is important to consider the concentrations in situ. For example, the flavan-3-ols (catechins), phenolic acids and resveratrol, among other compounds, have been reported to be contributors to the antioxidant properties of wine. However, the level of resveratrol is likely to be too low to be physiologically relevant (Leake 1998 ), as the levels of resveratrol are reported to be at least 100 times less than those of the other antioxidant components of (Frankel et al. 1995 ). In the case of chocolate, procyanidins and quercetin levels are equally disparate, because the formulation of the consumed product (i.e., semisweet baking bits) contains the equivalent of 20% cocoa. Therefore, the actual level of free quercetin consumed would be 5 mg compared with 557 mg of procyanidins.

Second, it is clear that additional studies are necessary to assess the physiological relevance of these molecules considering their chemical structure, their function as antioxidants in a relevant biological milieu and their bioavailability. When considering the relevance of quercetin and its glycosides as physiological antioxidants in chocolate, we must also consider the significance of the model in which the antioxidant capacity is evaluated. For example, in an in vivo model of oxidative stress in mouse, (+)-catechins were 100 times more efficient than quercetin in preventing the formation of liver chemiluminescence (Fraga et al. 1987 ). In other models in which quercetin was a more potent antioxidant, the concentrations of catechins were always the same order of magnitude (Jovanovic et al. 1994 , Rice-Evans et al. 1996 ).

It is clear that cocoa is a complex plant food that, in its raw state, contains a diverse mixture of flavonoids, including anthocyanins, flavonols such as quercetin and its glycosides (as reported by Lamuela-Raventos et al.) and the flavan-3-ols such as epicatechin, catechin and their related oligomers, the procyanidins. Some finished cocoa and chocolate products may well contain sufficient amounts of these interesting phytochemical antioxidants to favorably influence in vivo oxidant defense, and recent data from our group certainly support this hypothesis. The possibility that quercetin and related compounds are found in circulation in levels significant to contribute to the antioxidant protection observed after chocolate consumption is a matter that still must be studied.

	REFERENCES

TOP INTRODUCTION REFERENCES

 

1. Fraga C. G., Martino V. S., Ferraro G. E., Coussio J. D., Boveris A. Flavonoids as antioxidants evaluated by in vitro and in situ liver chemiluminescence. Biochem. Pharmacol. 1987;36:717-720[Medline]

2. Frankel E. N., Waterhouse A. L., Teissedre P. L. Principal phenolic phytochemicals in selected California wines and their antioxidant activity in inhibiting oxidation of human low-density lipoproteins. J Agric. Food Chem. 1995;43:890-894

3. Jovanovic S. V., Steenken S., Tosic M., Marjanovic B., Simic M. G. Flavonoids as antioxidants. J. Am. Chem. Soc. 1994;116:4846-4851

4. Leake D. S. Effects of flavonoids on the oxidation of low-density lipoproteins. Rice-Evans C. A. Packer L. eds. Flavonoids in Health and Disease 1998:253-276 Marcel Dekker New York, NY.

5. Rice-Evans C. A., Miller N. J., Paganga G. Structure-antioxidant activity relationships of flavonoids and phenolic acids. Free Radic. Biol. Med. 1996;20:933-956[Medline]

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