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GRAPE SKIN EXTRACT

(ENOCIANINA)

Source:Varieties ofVitis viniferaL. (Family
Vitaceae).

GENERAL DESCRIPTION

Grape skin extract or enocianina is the color-
ing matter derived from the skin of certain
varieties of the wine grape. It is commonly
obtained by acidic aqueous extraction of fer-
mented grape skin (or marc) after the juice has
been expressed from it.
The major producer of enocianina is Italy;
United States is a potential producer.

CHEMICAL COMPOSITION

The pigments present in enocianina are an-
thocyanins. They are glycosides of polyhy-
droxy derivatives of 2-phenylbenzopyrylium
salts. Their aglycones are generally called
anthocyanidins.1,2The most common antho-
cyanidins in grape skin extract are peonidin,
malvidin, delphinidin, and petunidin. The
grape anthocyanins are usually either mono-
glycosides or diglycosides.3,4Oligomeric an-
thocyanins have also been detected by MS
analysis.^5
In addition to anthocyanins, grape skin
extract contains plant acids (mainly tartaric
acid), tannins, sugars, amino acids, minerals,

and other constituents present in grapes. It

may also contain diluents used in processing.

Grapeskinanthocyaninsaresolubleinwater

and water–alcohol mixtures to yield red to

magenta solutions with an acidic pH (ca. 3).

ThecolorvarieswiththepH,fromredtopurple,

and finally to almost blue as the pH is changed

from1to8.Thepigmentsaremoststablebelow

pH3andarenotstableathigherpHvalues:they

are also sensitive to heat, oxygen, and light.6,7

PHARMACOLOGY AND BIOLOGICAL

ACTIVITIES

Grape skin extract obtained fromV. labrusca

has antihypertensive vasodilator effect.8,9The

same extract and others obtained from V.

viniferaare strong antioxidants that may be

beneficial as cardioprotective and neuropro-

tective (in Alzheimer’s disease) agents.9–11

Anthocyanins from grapes have been re-

portedtohaveantifungalactivities(e.g.,against

PenicilliumnotatumandAspergillusspecies)^12

andstrong‘‘vitaminP’’(bioflavonoids)activity,

strengtheningbloodcapillariesofguineapigs.^13

A grape anthocyanin (delphinidin-3-monoglu-

coside) has also been reported to inhibit the

growth ofLactobacillus acidophilus.^14

TOXICOLOGY

A tannic substance (leucocyanidin) present in

some grape juices has been reported to be

toxic to laboratory animals; symptoms includ-

ed cardiac failure and hepatic lesions.^15 Re-

342 Grape skin extract (enocianina)