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tannin, tannic acid, or gallotannic acid, astringent vegetable product found in a wide variety of plants. Sources include the bark of oak, hemlock, chestnut, and mangrove; the leaves of certain sumacs; and plant galls. Tannin is also present in tea, coffee, and walnuts. A solution of tannic acid is obtained from one of these natural sources by extraction with hot water; in particular, gallotannic acid is obtained from plant gall. Tannin varies somewhat in composition, having the approximate empirical formula C76H52O46. Tannic acid is a colorless to pale yellow solid; it is believed to be a glucoside in which each of the five hydroxyl groups of the glucose molecule is esterified with a molecule of digallic acid. Tannin is used in tanning animal skins to make leather; it transforms certain proteins of animal tissue into compounds that resist decomposition. It is also used in manufacturing inks, as a mordant in dyeing, and in medicine as an astringent and for treatment of burns.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



any of a group of phenol compounds that are widespread in plants and are capable of forming strong bonds with proteins and certain other natural polymers, such as cellulose and pectins.

Originally (late 18th century), the term “tannin” was applied to a mixture of substances extracted by water from a number of plants that was capable of transforming animal hides into leather. In modern usage, the term includes all naturally occurring compounds having molecular weights from 500 to 3,000 and containing a large number of phenolic hydroxyl groups. (In the Soviet Union, tannins of plant origin are also called tannides.)

Tannins are divided into two classes. The first comprises the tannins formed by a polyhydric alcohol, such as glucose, in which the hydroxyl groups are partially or completely esterified by gallic acid or related compounds. These tannins are referred to as hydrolyzable; an example is seen in structural formula I. The second includes the tannins formed through the condensation of such phenol compounds as catechins. These tannins are described as condensed; an example is seen in structural formula II.

Tannins are contained in galls and in bark, wood, and leaves and/or fruits of tannin plants. They are used in tanning leather, and they also serve as mordants in dyeing cotton fabrics. In medicine they are used as astringents. When used on burns, aqueous solutions of tannins bind the toxic protein products of tissue decomposition and facilitate healing. In the body, tannins can bind bacterial toxins, as well as toxic salts of silver, mercury, and lead.


Biokhimiia rastenii. Moscow, 1968. Chapter 22. (Translated from English.)
Zaprometov, M. N. Osnovy biokhimii fenol’nykh soedinenii. Moscow, 1974.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


(organic chemistry)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


any of a class of yellowish or brownish solid compounds found in many plants and used as tanning agents, mordants, medical astringents, etc. Tannins are derivatives of gallic acid with the approximate formula C76H52O46
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Naturally found in a large variety of both edible and inedible plants, tannins belong to a group of compounds called polyphenols, and are often produced by plants to protect against pests.
The ATE, a water-soluble extract from the Acacia mearnsii tree bark was obtained from UCL Tannin Pty (Ltd), South Africa, and used as the active ingredient or core material in the current study.
Interestingly, when the opposite type of tannin was put into Cabernet or Pinot wines, the panelists could not detect differences in dryness.
Wine alcohol treatments did not affect anthocyanin extraction but did increase tannin extraction.
Big, bold, dark fruits backed up with huge tannins. A great cabernet, but needs a long decant.
Tannin extract was obtained from mangium bark, following a previously reported extraction procedure (Hendrik et al.
Full-to-medium body with rich ripe medium tannins and medium-plus acid to a ripe, full-body, flavorful, spicy finish.
(1997), soluble pectins can form covalent and non-covalent bonds with the soluble tannin molecules, forming insoluble tannin polymers and removing the astringency of the fruit.
Interactions of proteins with sorghum tannin: Mechanism, specificity and significance.
Medium body, tannins, this is a very well structured, mellow, long-lasting flavour with smooth, light, velvety tannins, accents of earth, tobacco and spice as they linger on the tangy finish.
This study mainly focused on the effect of tannins against both reference and clinical strains of MRSA by means of antimicrobial assays and a next-generation sequencing (NGS) approach.