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1 Departament de Nutrició i Bromatologia, CERTA, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII s/n, 08028 Barcelona, Spain, E-mail: lamuela{at}farmacia.far.ub.es
2 Nutrexpa Group Lepanto 410 08025 Barcelona, Spain
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INTRODUCTION |
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 TOP INTRODUCTION REFERENCES |
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Rein and colleagues (1)
reported that cocoa might
contribute to the plasma total antioxidant capacity because of its high
content of flavan-3-ols (epicatechin). The consumption of cocoa by the
Dutch population is relatively high compared with that of other groups,
and it has been considered to be an important source of flavonoids
(epicatechin) (2)
. However, other phenolic compounds,
although present in lower concentrations, may also be very important
because of their high antioxidant activity. Therefore, the role of
these phenolic compounds in human health should be carefully studied.
In addition to epicatechin, cocoa appears to be an important source of other dietary polyphenols, including catechin and quercetin. The flavonol quercetin is mainly present in fruits and vegetables, although apples and onions constitute the main sources of this compound.
Cocoa powder extract is a potent antioxidant that protects the
low-density lipoprotein (LDL) cholesterol particle from becoming
atherogenic by preventing it from becoming oxidatively modified
(3)
. In fact, quercetin has been shown to be one of the
most effective polyphenols in protection of LDL from modification
(4
,5)
. Eberhardt and colleagues (6)
recently
showed that extracts from the whole apple reduced the proliferation of
tumor cells significantly more than extracts from apples without skins.
It appears that the major polyphenols present in apple skin include the
flavonol glycosides, which are good antioxidants and appear to be
responsible for the observed antitumor effects (6)
.
Until now, the antioxidant capacity of cocoa has been attributed only
to the epicatechin content. However, quercetin compounds might also be
important contributors to the total polyphenols present in cocoa and
convey potential health benefits. Our group has identified and
quantified three flavonols, isoquercitrin, quercetin 3-glucuronide and
quercetin, in cocoa powder using HPLC-DAD coupled with HPLC-MS.
The major flavonols in cocoa are isoquercitrin (23 mg/100 g), quercetin
3-glucuronide (5 mg/100 g) and quercetin (2 mg/100 g). In general,
cocoa powder contains 30 mg flavonols/100 g. The work by de Whalley and
colleagues (7)
demonstrates that quercetin is the most
effective flavonoid for the preservation of endogenous 
-tocopherol
in LDL cholesterol. Thus, we believe these compounds (flavonols) should
be included in future studies.
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REFERENCES |
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TOPINTRODUCTIONREFERENCES |
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1.
Rein D., Lotito S., Holt R. R., Keen C. L., Schmitz H. H., Fraga C. G. Epicatechin in human plasma: In vivo determination and effect of chocolate consumption on plasma oxidation status. J. Nutr. 2000;130:2109S-2114S
2. Arts I.C.W., Hollman P.C.H., Kromhout D. Chocolate as a source of tea flavonoids. Lancet 1999;354:488[Medline]
3. Waterhouse A. L., Shirley J. R., Donovan J. L. Antioxidants in chocolate. Lancet 1996;348:834[Medline]
4. 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]
5.
Lamuela-Raventós R. M., Covas M. I., Fitó M., Marrugat J., de la Torre-Boronat M. C. Detection of dietary antioxidant phenolic compounds in LDL. Clin. Chem. 1999;45:1870-1872
6. Eberhardt M. V., Lee C. Y., Liu R. H Antioxidant activity of fresh apples. Nature 2000;405:903-904[Medline]
7. de Whalley C. V., Rankin S. M., Hoult J.R.S., Jessup W., Leake D. S. Flavonoids inhibit the oxidative modification of LDL by macrophages. Biochem. Pharmacol. 1990;39:1743-1550[Medline]
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