Tannins
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Tannins
Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with various macromolecules. The term ''tannin'' (from scientific French ''tannin'', from French ''tan'' "crushed oak bark", ''tanner'' "to tan", cognate with English ''tanning'', Medieval Latin ''tannare'', from Proto-Celtic ''*tannos'' "oak") refers to the abundance of these compounds in oak bark, which was used in tanning animal hides into leather. The tannin compounds are widely distributed in many species of plants, where they play a role in protection from predation (acting as pesticides) and might help in regulating plant growth. The astringency from the tannins is what causes the dry and puckery feelin ...
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Tannin Heap
Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with various macromolecules. The term ''tannin'' (from scientific French ''tannin'', from French ''tan'' "crushed oak bark", ''tanner'' "to tan", cognate with English ''tanning'', Medieval Latin ''tannare'', from Proto-Celtic ''*tannos'' "oak") refers to the abundance of these compounds in oak bark, which was used in tanning animal hides into leather. The tannin compounds are widely distributed in many species of plants, where they play a role in protection from predation (acting as pesticides) and might help in regulating plant growth. The astringency from the tannins is what causes the dry and puckery feeling in th ...
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Hydrolyzable Tannin
A hydrolysable tannin or pyrogallol-type tannin is a type of tannin that, on heating with hydrochloric or sulfuric acids, yields gallic or ellagic acids. At the center of a hydrolysable tannin molecule, there is a carbohydrate (usually D-glucose but also cyclitols like quinic or shikimic acids). The hydroxyl groups of the carbohydrate are partially or totally esterified with phenolic groups such as gallic acid in gallotannins or ellagic acid in ellagitannins. Hydrolysable tannins are mixtures of polygalloyl glucoses and/or poly-galloyl quinic acid derivatives containing in between 3 up to 12 gallic acid residues per molecule. Hydrolysable tannins are hydrolysed by weak acids or weak bases to produce carbohydrate and phenolic acids. Examples of gallotannins are the gallic acid esters of glucose in tannic acid (C76H52O46), found in the leaves and bark of many plant species. Hydrolysable tannins can be extracted from different vegetable plants, such as chestnut wood ...
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Proanthocyanidin
Proanthocyanidins are a class of polyphenols found in many plants, such as cranberry, blueberry, and grape seeds. Chemically, they are oligomeric flavonoids. Many are oligomers of catechin and epicatechin and their gallic acid esters. More complex polyphenols, having the same polymeric building block, form the group of Condensed tannin, condensed tannins. Proanthocyanidins were discovered in 1947 by Jacques Masquelier, who developed and patented techniques for the extraction of oligomeric proanthocyanidins from pine bark and grape seeds. Proanthocyanidins are under preliminary research for the potential to reduce the risk of urinary tract infections (UTIs) by consuming cranberries, grape seeds or red wine. Distribution in plants Proanthocyanidins, including the lesser bioactive and bioavailable polymers (four or more catechins), represent a group of condensed flavan-3-ols, such as procyanidins, prodelphinidins and propelargonidins. They can be found in many plants, most notably ...
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Polyphenol
Polyphenols () are a large family of naturally occurring phenols. They are abundant in plants and structurally diverse. Polyphenols include phenolic acids, flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning (leather), tanning garments. Etymology The name derives from the Ancient Greek word (, meaning "many, much") and the word ‘phenol’ which refers to a chemical structure formed by attachment of an aromatic benzenoid (phenyl) ring to a hydroxyl (-OH) group (hence the ''-ol'' suffix). The term "polyphenol" has been in use at least since 1894. Definition Polyphenols are natural products with "one or several hydroxyl groups on aromatic rings", including four principal classes: phenolic acids, flavonoids, stilbenes, and lignans. Flavonoids can be grouped as flavones, flavonols, flavanols, flavanones, isoflavones, proanthocyanidins, and anthocyanins. Particularly abundant flavanoids in foods are catechin (tea, frui ...
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Phloroglucinol
Phloroglucinol is an organic compound with the formula C6H3(OH)3. It is a colorless solid. It is used in the organic synthesis, synthesis of pharmaceuticals and explosives. Phloroglucinol is one of three isomeric benzenetriols. The other two isomers are hydroxyquinol (1,2,4-benzenetriol) and pyrogallol (1,2,3-benzenetriol). Phloroglucinol, and its benzenetriol isomers, are still defined as "natural phenol, phenols" according to the IUPAC official nomenclature rules of chemical compounds. Many such monophenolics are often termed polyphenols. The enzyme is biosynthesized by phloroglucinol synthase. Synthesis and occurrence In 1855, phloroglucinol was first prepared from phloretin by the Austrian chemist Heinrich Hlasiwetz (1825–1875). A modern synthesis of phloroglucinol involves hydrolysis of benzene-1,3,5-triamine and its derivatives. Representative is the following route from 1,3,5-Trinitrobenzene, trinitrobenzene. : The synthesis is noteworthy because ordinary aniline deriv ...
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Phloroglucin
Phloroglucinol is an organic compound with the formula C6H3(OH)3. It is a colorless solid. It is used in the synthesis of pharmaceuticals and explosives. Phloroglucinol is one of three isomeric benzenetriols. The other two isomers are hydroxyquinol (1,2,4-benzenetriol) and pyrogallol (1,2,3-benzenetriol). Phloroglucinol, and its benzenetriol isomers, are still defined as "phenols" according to the IUPAC official nomenclature rules of chemical compounds. Many such monophenolics are often termed polyphenols. The enzyme is biosynthesized by phloroglucinol synthase. Synthesis and occurrence In 1855, phloroglucinol was first prepared from phloretin by the Austrian chemist Heinrich Hlasiwetz (1825–1875). A modern synthesis of phloroglucinol involves hydrolysis of benzene-1,3,5-triamine and its derivatives. Representative is the following route from trinitrobenzene. : The synthesis is noteworthy because ordinary aniline derivatives are unreactive toward hydroxide. Because the ...
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Tannic Acid
Tannic acid is a specific form of tannin, a type of polyphenol. Its weak acidity (Acid dissociation constant, pKa around 6) is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C76H52O46, which corresponds with decagalloyl glucose, but in fact it is a mixture of polygalloyl glucoses or polygalloyl quinic acid esters with the number of gallic acid, galloyl moieties per molecule ranging from 2 up to 12 depending on the plant source used to extract the tannic acid. Commercial tannic acid is usually extracted from any of the following plant parts: Tara pods (''Caesalpinia spinosa''), gallnuts from ''Rhus semialata'' or ''Quercus infectoria'' or Sicilian sumac leaves (''Rhus coriaria''). According to the definitions provided in external references such as international pharmacopoeia, Food Chemicals Codex and FAO-WHO tannic acid monograph only tannins obtained from the above-mentioned plants can be considered as tanni ...
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Gallic Acid
Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6 H2( OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. It is a white solid, although samples are typically brown owing to partial oxidation. Salts and esters of gallic acid are termed "gallates". Its name is derived from oak galls, which were historically used to prepare tannic acid. Despite the name, gallic acid does not contain gallium. Isolation and derivatives Gallic acid is easily freed from gallotannins by acidic or alkaline hydrolysis. When heated with concentrated sulfuric acid, gallic acid converts to rufigallol. Hydrolyzable tannins break down on hydrolysis to give gallic acid and glucose or ellagic acid and glucose, known as gallotannins and ellagitannins, respectively. Biosynthesis Gallic acid is formed from 3-dehydroshikimate by the action of the enzyme shikimat ...
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Tanning (leather)
Tanning, or hide tanning, is the process of treating Skinning, skins and Hide (skin), hides of animals to produce leather. A tannery is the place where the skins are processed. Historically, vegetable based tanning used tannin, an acidic chemical compound derived from the bark of certain trees, in the production of leather. An alternative method, developed in the 1800s, is chrome tanning, where chromium salts are used instead of natural tannins. History Tanning hide into leather involves a process which permanently alters the protein structure of skin, making it more durable and less susceptible to decomposition and coloring. The place where hides are processed is known as a ''tannery''. The English word for tanning is from the medieval Latin verb , from the noun (oak bark). This term may be derived from a Celtic word related to the Proto-Indo-European *' meaning 'fir tree'. (The same root is the source for Old High German meaning 'fir', related to modern German ''Tannenb ...
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Astringent
An astringent (sometimes called adstringent) is a chemical that shrinks or constricts body tissues. The word derives from the Latin '' adstringere'', which means "to bind fast". Astringency, the dry, puckering or numbing mouthfeel caused by the tannins in unripe fruits, lets the fruit mature by deterring eating. Tannins, being a kind of polyphenol, bind salivary proteins and make them precipitate and aggregate, producing a rough, "sandpapery", or dry sensation in the mouth. Smoking tobacco is also reported to have an astringent effect. In a scientific study, astringency was still detectable by subjects who had local anesthesia applied to their taste nerves, but not when both these and the trigeminal nerves were disabled. Uses In medicine, astringents cause constriction or contraction of mucous membranes and exposed tissues and are often used internally to reduce discharge of blood serum and mucous secretions. This can happen with a sore throat, hemorrhages, diarrhe ...
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Astringency
An astringent (sometimes called adstringent) is a chemical that shrinks or constricts body tissues. The word derives from the Latin '' adstringere'', which means "to bind fast". Astringency, the dry, puckering or numbing mouthfeel caused by the tannins in unripe fruits, lets the fruit mature by deterring eating. Tannins, being a kind of polyphenol, bind salivary proteins and make them precipitate and aggregate, producing a rough, "sandpapery", or dry sensation in the mouth. Smoking tobacco is also reported to have an astringent effect. In a scientific study, astringency was still detectable by subjects who had local anesthesia applied to their taste nerves, but not when both these and the trigeminal nerves were disabled. Uses In medicine, astringents cause constriction or contraction of mucous membranes and exposed tissues and are often used internally to reduce discharge of blood serum and mucous secretions. This can happen with a sore throat, hemorrhages, diarrhea, and p ...
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