Tannic acid is the generic name of a family of polyphenolic organic compounds, also known as hydrolyzable tannins. The hypothetical chemical formula of a commercial tannic acid is C76H52OR46. Tannic acids are also known as gallotanical acids.
They are widely distributed in nature, found mainly in the bark and fruits of some trees such as chestnut oak and sweet chestnuts, among others..
A tannic acid is a polyphenol of high molecular weight and of variable composition formed by the esterification of gallic acid and 3-galloylgalic acid with glucose. A tannic acid must be differentiated from a condensed tannin, since the latter come from different compounds.
According to sources consulted, hydrolyzable tannins or tannic acids are not found in tea. Tannic acids are used to stabilize beverages such as beer and wine, helping to eliminate their turbidity..
Due to their antimicrobial action, they have several medicinal uses. They have been used to treat laryngitis, ulcers, bleeding, diarrhea, skin irritations, among other conditions. They are also used in veterinary treatments.
Tannic acids are used for tanning and coloring animal skins to obtain water and heat resistant leather. Additionally, researchers are constantly finding new uses for tannic acids..
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Hydrolyzable tannic acids or tannins have a center formed by a polyhydric alcohol, such as glucose, and hydroxyl groups esterified by gallic acid (3,4,5-trihydroxy-benzoic acid) or hexahydroxydiphenic acid, therefore they contain a large amount of -OH groups attached to benzene rings.
- Tannic acids
- Hydrolyzable tannins
Light yellow to brown amorphous solids.
C76H52OR46: 1701.2 g / mol
200 ºC
198.9 ºC (open cup method)
526.7 ºC
Greater than 1 to 20 ºC
Miscible with water. Very soluble in alcohol and acetone.
Insoluble in ether, benzene, carbon tetrachloride and chloroform.
Tannic acids precipitate proteins because they react with the -SH groups of some of the amino acids present in them..
Hydrolysis of tannic acids with the enzyme tannase generates glucose, gallic acid, and gallic acid.
With ferric salts they give bluish-black compounds.
Hydrolyzable tannins or tannic acids are obtained from various plant sources generally by extraction with organic solvents (such as acetone or ethyl acetate) or extraction with water..
They are extracted, for example, from chestnut seed pods (Castanea sativa), from the Turkish gall (Quercus infectoria), Chinese gall (Rhus semialata), tare (Caesalpina spinosa) and myrobalan nuts (Terminalia chebula).
Tannic acid works as a stabilizer in beer through precipitation, as it makes the polyphenol / protein ratio more balanced..
It is used at concentrations of 2 to 6 g per 100 L. It acts by precipitating the proteins that cause turbidity in beer, since it binds amino acids with exposed -SH groups. Once the material has precipitated, the beer is centrifuged or transferred by careful decantation.
The most widely used tannic acid for this purpose is gallotannin, which also removes some metals and other protein-bound polyphenols.
It is said to be effective against the appearance of rancid taste and against instability towards light and that it acts as an antioxidant. However, according to some, it acts negatively on beer foam.
Tannic acid is also used to precipitate unstable wine proteins, improving its colloidal stability. Unstable proteins produce cloudiness when the drink is cooled.
Wines may contain hydrolyzable tannins released from oak barrels during the maturation period or by direct addition by the wine maker..
For example, one of the usual doses of tannic acid for red wine is 2 g / L. It gives this product an astringent sensation.
Tannic acid exhibits several characteristics that can help against diseases. Among its properties are its astringent, antibacterial, antihistamine, antioxidant, antienzymatic, antitussive and antimutagenic action..
Due to the properties mentioned it is used to treat ulcers, diarrhea, to stop bleeding, heal wounds, burns, ingrown nails, toothaches, fevers, skin rashes and irritations caused by diapers..
Inhibits the growth of bacteria such as Bacteriodes fragilis, Clostridium perfringens Y Escherichia coli that can cause diarrhea or peritoneal infections in certain cases.
Medicinal grade tannic acid is used to treat laryngitis, tonsillitis and hemorrhoids.
Its presence in certain medications imparts slow-release properties of the active ingredient, which is beneficial for a slow dosage of the drug in the body..
Tannic acid salts or tannates are used in antihistamine and antitussive formulations.
Tanalbine is a complex made up of tannic acid and certain proteins. It is used to treat diarrhea and bacterial or fungal infections. It does not cause irritation of the digestive tract and is resistant to the gastric environment.
In this application, tannic acid acts in several ways:
- Coagulates proteins in the intestine.
- Stop water loss.
- It is attached to the surface of yeasts, fungi or bacteria, preventing their colonization.
- Adheres to the membrane of the intestinal walls acting as a barrier.
On the other hand, the hydrolysis of tannic acids produces gallic acid that is also widely used in the pharmaceutical industry..
Due to its astringent capacity, tannic acid is used to treat diarrhea in animals..
Its astringent power is due to the fact that it forms a provisional film of coagulated proteins on the surface of the intestinal mucosa, which effectively protects it from caustic agents..
In addition, this film numbs the sensory nerve endings present in the mucosa that are responsible for any reflex hyperexcitability..
The protein precipitate is relatively impervious to the passage of fluids in any direction, so it is very effective in combating the condition.
Tannic acids are used for tanning animal hides and skins.
The phenolic -OH groups that tannic acids have in great quantity form very effective cross-links with leather proteins, which increases their stability against water, bacteria, heat and abrasion..
Tannic acids extracted from Chinese and Turkish gall plants are used as wool dyes and black hair dyes.
It is used as a flavor additive. The use of tannic acid up to a maximum level of 15 mg / Kg is safe for all animals. Its use as a feed additive does not constitute a safety risk for consumers.
Some researchers found that tannic acids can be used to coat polypropylene spacers in lithium ion batteries..
Due to their large number of -OH groups, tannic acids make the surface of these separators more hydrophilic, which increases the electrolyte retention ability and ionic conductivity of the separator..
Increased ionic conductivity improves battery performance, especially battery power.
Scientists in the area of medicine developed a nanoparticle made up of tannic acid that contains an encapsulated anti-cancer drug (paclitaxel).
It was found that the nanoparticle shows a great ability to efficiently encapsulate the drug and achieve high drug delivery efficiency at specific intestinal sites..
The nanoparticle with tannic acid demonstrated a significant chemotherapeutic effect against cancer tumors after oral administration..
Tannic acid can interfere with the growth of bacteria normally contained in the intestinal tract of the human or animal organism..
Tannic acid should not be used continuously or in high doses because it adversely affects the absorption of iron and other minerals..
In addition, its ingestion in high quantities can reduce the effectiveness of digestive enzymes..
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