Hydrolysable tannin
Encyclopedia
A hydrolyzable tannin or pyrogallol
-type tannin is a type of tannin
that, on heating with hydrochloric
or sulfuric acid
s, yields gallic
or ellagic acid
s.
At the center of a hydrolyzable tannin molecule
, there is a carbohydrate
(usually D-glucose but also cyclitol
s like quinic
or shikimic acid
s). The hydroxyl groups of the carbohydrate are partially or totally esterified with phenolic groups such as gallic acid
in gallotannin
s or ellagic acid
in ellagitannin
s. 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.
Hydrolyzable tannins are hydrolyzed by weak acids or weak bases to produce carbohydrate and phenolic acid
s.
Examples of gallotannins are the gallic acid
ester
s of glucose
in tannic acid
(C76H52O46), found in the leaves
and bark
of many plant
species.
(epigallitannins), are inhibitors of HIV replication. 1,3,4-Tri-O-galloylquinic acid, 3,5-di-O-galloyl-shikimic acid, 3,4,5-tri-O-galloylshikimic acid, punicalin, punicalagin
inhibited HIV replication in infected H9 lymphocyte
s with little cytotoxicity. Two compounds, punicalin and punicacortein C, inhibited purified HIV reverse transcriptase
.
Hydrolysable tannins have shown also potential antibacterial effects against Helicobacter pylori
.
In the past few years, hydrolysable tannins have also been studied for their potential effects against cancer through different mechanisms
.
Pyrogallol
Pyrogallol or benzene-1,2,3-triol is a benzenetriol. It is a white crystalline powder and a powerful reducing agent. It was first prepared by Scheele 1786 by heating gallic acid. An alternate preparation is heating para-chlorophenoldisulphonic acid with potassium hydroxide.When in alkaline...
-type tannin is a type of tannin
Tannin
A tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.The term tannin refers to the use of...
that, on heating with hydrochloric
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
or sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
s, yields gallic
Gallic acid
Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of...
or ellagic acid
Ellagic acid
Ellagic acid is a natural phenol antioxidant found in numerous fruits and vegetables including blackberries, raspberries, strawberries, cranberries, walnuts, pecans, pomegranates, wolfberry and other plant foods...
s.
At the center of a hydrolyzable tannin molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
, there is a carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
(usually D-glucose but also cyclitol
Cyclitol
Cyclitols are cycloalkanes containing one hydroxyl group on three or more ring atoms. They are cyclic polyols. Cyclitols are one of the compatible solutes which are formed in a plant as a response to salt or water stress...
s like quinic
Quinic acid
Quinic acid is a cyclitol, a cyclic polyol. It is a crystalline acid obtained from cinchona bark, coffee beans, and other plant products and made synthetically by hydrolysis of chlorogenic acid. Quinic acid is also implicated in the perceived acidity of coffee...
or shikimic acid
Shikimic acid
Shikimic acid, more commonly known as its anionic form shikimate, is an important biochemical metabolite in plants and microorganisms. Its name comes from the Japanese flower shikimi , from which it was first isolated....
s). The hydroxyl groups of the carbohydrate are partially or totally esterified with phenolic groups such as gallic acid
Gallic acid
Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of...
in gallotannin
Gallotannin
A gallotannin is a class of molecules belonging to the hydrolysable tannins. Gallotannins are polymers formed when gallic acid, a polyphenol monomer, esterifies and binds with the hydroxyl group of a polyol carbohydrate such as glucose.-Metabolism:...
s or ellagic acid
Ellagic acid
Ellagic acid is a natural phenol antioxidant found in numerous fruits and vegetables including blackberries, raspberries, strawberries, cranberries, walnuts, pecans, pomegranates, wolfberry and other plant foods...
in ellagitannin
Ellagitannin
The ellagitannins are a diverse class of hydrolyzable tannins, a type of polyphenol formed primarily from the oxidative linkage of galloyl groups in 1,2,3,4,6-Pentagalloyl glucose...
s. Hydrolysable tannins are mixtures of polygalloyl glucoses and/or poly-galloyl quinic acid
Quinic acid
Quinic acid is a cyclitol, a cyclic polyol. It is a crystalline acid obtained from cinchona bark, coffee beans, and other plant products and made synthetically by hydrolysis of chlorogenic acid. Quinic acid is also implicated in the perceived acidity of coffee...
derivatives containing in between 3 up to 12 gallic acid residues per molecule.
Hydrolyzable tannins are hydrolyzed by weak acids or weak bases to produce carbohydrate and phenolic acid
Phenolic acid
Phenolic acids are a type of organic compounds. Included in that class are substances containing a phenolic ring and an organic carboxylic acid function ....
s.
Examples of gallotannins are the gallic acid
Gallic acid
Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of...
ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
s of glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
in tannic acid
Tannic acid
Tannic acid is a specific commercial form of tannin, a type of polyphenol. Its weak acidity is due to the numerous phenol groups in the structure...
(C76H52O46), found in the leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
and bark
Bark
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
of many plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
species.
Uses
Tannins, including gallo and ellagic acidEllagic acid
Ellagic acid is a natural phenol antioxidant found in numerous fruits and vegetables including blackberries, raspberries, strawberries, cranberries, walnuts, pecans, pomegranates, wolfberry and other plant foods...
(epigallitannins), are inhibitors of HIV replication. 1,3,4-Tri-O-galloylquinic acid, 3,5-di-O-galloyl-shikimic acid, 3,4,5-tri-O-galloylshikimic acid, punicalin, punicalagin
Punicalagin
Punicalagin is an ellagitannin, a polyphenol compound which are isomers of 2,3--hexahydroxydiphenoyl-4,6--gallagyl-D-glucose, hydrolysable tannins with a molecular weight of 1084. They are found in forms alpha and beta in pomegranates...
inhibited HIV replication in infected H9 lymphocyte
Lymphocyte
A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...
s with little cytotoxicity. Two compounds, punicalin and punicacortein C, inhibited purified HIV reverse transcriptase
Reverse transcriptase
In the fields of molecular biology and biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into single-stranded DNA. It also helps in the formation of a double helix DNA once the RNA has been reverse...
.
Hydrolysable tannins have shown also potential antibacterial effects against Helicobacter pylori
Helicobacter pylori
Helicobacter pylori , previously named Campylobacter pyloridis, is a Gram-negative, microaerophilic bacterium found in the stomach. It was identified in 1982 by Barry Marshall and Robin Warren, who found that it was present in patients with chronic gastritis and gastric ulcers, conditions that were...
.
In the past few years, hydrolysable tannins have also been studied for their potential effects against cancer through different mechanisms
.