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Dietetic and Pharmaceutical Raw Materials
RED WINE PROANTHOCYANIDINS
A Summary
The term "Polyphenols"
describes a number of natural compounds with a dietetically attractive effect.
They have in common that they contain hydroxyphenyl groups (1). In red wine
basically two types of these polyphenols occur, the non-flavonoid type on the
one hand bearing hydroxy phenyl moieties predominantly as caffeic acid (2)
(esterified with tartaric acid as caftaric acid) and - more important - the
flavonoid type. The latter contain either flavanol (4), flavylium (5) or flavon
(6) units. Examples for (4) is catechin (and the diastereomeric epicatechin),
for (5) cyanidin (an anthocyanidin), for (6) quercetin.
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Hydroxyphenyl residue |
Caffeic acid |
Gallic acid |
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Catechin,
Epicatechin |
Cyanidin: R1,R3=OH; R2=H |
Quercetin |
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Malividin: R1, R2=OCH3; R3=OH |
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Origin of the non-flavonoid
polyphenols of red wine is the fruit pulp of the grape berry, origin of the flavonoid
polyphenols are seeds and skins of the grapes which release these compounds
into the grape juice during fermentation (SINGLETON, 1992; BOURZEIX, 1986). The
main quantity of the (colorless) flavanols are found in the grape seeds, the
skins contain next to flavanols also the color imparting anthocyanins, that is,
glucosides of anthocyanidins with a flavylium ion as basic unit. Red wine
anthocyanidins are predominantly cyanidin and malvidin (4). Flavons (rutin,
quercetin (5), myricetin) do also occur in red wine (FRANKEL, 1995), they are
probably oxidation products of flavanols. Flavanols are the main constituents
of the polyphenols found in red wine, namely catechin and (the diastereomeric)
epicatechin and oligomers of the two in which the epicatechin units are
frequently esterified with gallic acid (6).
(The situation with white
grapes is essentially the same as with red grapes except that (color imparting)
anthocyanidins are absent. White wine itself contains only non-flavonoid
polyphenols as white grape must is not allowed to stay in contact with skins
and seeds for any time before fermentation so that no flavonoid polyphenols can
be released into the must).
Only the flavanols (not the
flavons) are inclined towards oligomerization and are therefore sometimes
referred to as "Pycnogenols" (Greek, meaning roughly
"condensor"). The term has a more commercial rather than scientific
meaning. The oligomeric flavanols are also called proanthocyanidins as the
colorless substances yield colored anthocyanidins when exposed to acid and air.
In case of red wine one often speaks of procyanidin as the red wine
proanthocyanidins are indeed predominantly procyanidins forming thus in
oxidative acidic hydrolysis specifically cyanidin. (Leuko-anthocyanidins are
not identical with pro-anthocyanidins: the former are MONOmeric
3,4-flavan-DIOLS, the latter are OLIGOmeric 3-flavanOLS, both are not coloured,
both form coloured anthocyanidins on oxidation).
In general one may say that
the 3-flavanols: (epi-)catechin, gallo(epi)catechin, fisetinidol, robinetinidol
oligomerize in plants into the proanthocyanidins: procyanidin, prodelphinidin,
profisetinidin, prorobetinidin, which yield in vitro on acidic oxidative
hydrolysis the corresponding anthocyanidins: cyanidin, delphinidin,
fisetinidin, robetinidin. Specifically in red wine one may say that
(epi)catechin oligomerizes into procyanidin, which on acidic, oxydative
hydrolysis yields cyanidin (PORTER, 1992).
Pro-anthocyanidins do occur
also in other plants and plant parts, for instance in bark of conifers
(MASQUELIER, 1980) and in fruits (LEA, 1992). They are in low concentration
important for the flavor of wine, fruits and fruit juices. Their taste depends
on the degree of oligomerization. Up to a oligomerization degree of 4 (the
actual pro-anthocyanidins) a bitter note predominates, at oligomerization
beyond 4 the taste is astringent as in sloes and quinces (for the higher
oligomers the designation tannin is also appropriate) (LEA, 1992).
Catechins und
pro-anthocyanidins are very potent free radical scavengers. This is the basis
of their antioxidative effect (CHENIER, 1992). The term "French
paradox" refers to the observation that deaths caused by coronary heart
desease are less common in
In red wine occasionally the compound Resveratrol is found in low concentration
(in the ppm range). Resveratrol is a phytoalexin, that is, a compound formed by
plants in defense of fungus attacks. It therefore occurs in red wine only if
the grapes had before been infected by the mould "Botrytis"
("noble rottenness") an infection desired by vintners as it destroys
the grape skin and thus allows evaporation (and that is concentration) of the
grape juice. Resveratrol is anticancerogenic, apparently Because it is
converted into the toxic compound Piceatannol by an enzyme which occurs in
cancer cells only (POTTER, 2002; WIEDER, 2001).
In certain plants Resveratrol is formed independently of fungus infections.
Thus it is possible to prepare an extract from certain Polygonum species
containing as much as 5% Resveratrol.
References
BOURZEIX, M. et al. 1986:
Étude des catecéchines et des procyanidols de la grappe de raisin, du vin et
d'autres dérivés de la vigne. Bulletin de L'O.I.V, 1986, 669-670
CHENIER, V. et al., 1992:
Structure of Procyanidin Oligomers isolated from Grape Seeds in Relation to
Some of their Chemical Properties, p. 281-294, in: Plant Polyphenols, ed. R. W.
Hemingway, P.E. Laks, Plenum Press, 1992
FRANKEL, E.N. et al., 1993
(I): Inhibition of oxidation of human low-density lipoprotein by phenolic
substances. The Lancet, 341, Feb. 20, 1993, 454-457
FRANKEL, E.N. et al., 1993
(II): Inhibition of human LDL oxidation by resveratrol. The Lancet, 341, April
24, 1993, 1103-1104
FRANKEL, E.N. et al., 1995:
Principal Phenolic Phytochemicals in Selected
KINSELLA, J.E., et al.:
1993: Possible Mechanisms for the Protective Role of Antioxidants in Wine and
Plant Foods. Food Technology, April 1993, 35-39
LEA, A.G.H., 1992: Flavor,
Color and Stability in Fruit Products: The Effect of Polyphenols, p. 827-847,
in: Plant Polyphenols, ed. R. W. Hemingway, P.E. Laks, Plenum Press, 1992
MASQUELIER, J., 1980:
Pycnogenols: Recent Advances in the Therapeutical Activity of Procyanidins. In:
J.L. Beal and E. Reinhard, Natural Products as Medicinal Agents
MAXWELL, S. et al., 1994: Red
wine and antioxidant activity in serum. Lancet 344, 193-194
PERCHELLET, J.P. et al.,
1992: Antitumor Promoting Activities of Tannic Acid, Ellagic Acid, and several
Gallic Acid Derivatives in Mouse Skin, p. 783-801, in: Plant Polyphenols, ed.
R. W. Hemingway, P.E. Laks, Plenum Press, 1992
PORTER, L.J., 1992:
Structure and Chemical Proeprties of the Condensed Tannins, p. 245-258, in:
Plant Polyphenols, ed. R. W. Hemingway, P.E. Laks, Plenum Press, 1992
POTTER, G.A. et al., 2002:
The cancer preventive agent resveratrol is converted to the anticancer agent
piceatannol by the cytochrome P450 enzyme CYP1B1. British Journal of Cancer,
86, 774-778 (04. Mar 2002)
RENAUD, S. et al., 1992:
Wine, Alcohol, Platelets, and the French Paradox for Coronary Heart Desease.
Lancet 1992, 339, 1523-1526 St. LEGER et al., 1979: Factors associated with
cardia mortality in developed countries with particular reference to the
consumption of wine. Lancet 1979, May 12, 1017-20
SINGLETON, V.L., 1992: Tannins
and the Qualities of Wines, p. 859-880, in: Plant Polyphenols, ed. R. W.
Hemingway, P.E. Laks, Plenum Press, 1992
STAVRIC,
B., 1994: Quercetin in Our Diet: From potent Mutagen to Probable
Anticarcinogen.
WIEDER, T., et al., 2001: Piceatannol, a hydroxylated analog of the
chemopreventive agent resveratrol, is a potent inducer of apoptosis in the
lymphoma cell line BJAB and in primary, leukemic lymphoblasts. Leukemia,
November 2001, Vol 15, No. 11 pp. 1735-1742
