Таниновая кислота

Описание

Tannic acid is a naturally occurring plant polyphenol and can be found in practically all aerial plant tissues. Tannic acid was historically used for the treatment of diarrhea, topically to dress skin burns and rectally for treatment of unspecified rectal disorders. Pharmaceutical use of tannic acid is discontinued due to safer and better alternatives.
An unusually high incidence of esophageal cancer has been noted in areas of South Africa, where a sorghum rich in tannins is consumed. A positive relation has been observed between the tannin content of the sorghum and the incidence of esophageal cancer.

Химические свойства

Tannic acid, C₁₄H₁₀O₉, also known as digallic acid, tannin, and gallotannin, is a yellowish powder that decomposes at 210°C (410°F). Tannic acid is derived from nutgalls. It is soluble in water and alcohol,and is insoluble in acetone and ether. Tannic acid is used in tanning,textiles, and as an alcohol denaturant. An amorphous form of tannic acid, also known as pentadigalloylglucose, exists with the formula C₇₆H₅₂O₄₆. It is a yellowish to brownish powder that is very soluble in alcohol and ether.It also decomposes between 210 and 215°C (410 and 419 °F). This form is used to clarify wine or beer, as a reagent,and as a mordant in dyeing.

Вхождение

Reported found in Quercus oliver and related species; Tara (Caesalpinia spinosa); and various sumac species, including Rhus semialata, R. coriaria, R. glabra and R. typhia.

Использование

Tannic Acid is a sequestrant that refers to a mixture of hydrolyzable tannins of a more complex structure than gallic acid. it is used in clarifying beer and wine. see tannins.

Подготовка

Tannic acid is obtained by solvent extraction from the nutgalls or the excrescences that form on the young twigs of Quercus olivier and allied species of Quercus L.; from the seed pods of Tara (Caesalpinia spinosa); or from the nutgalls of various sumac species, including Rhus semialata, R. coriaria, R. glabra and R. typhia.

Определение

tannic acid: A yellowish complexorganic compound present in certainplants. It is used in dyeing as a mordant.

Общее описание

Light yellow to tan solid with a faint odor. Sinks and mixes with water.

Реакции воздуха и воды

Water soluble. Gradually darkens on exposure to air and/or light

Профиль реактивности

Glycerite decomposes at 210° to carbon dioxide and pyrogallol, which can form irritating vapors [USCG, 1999]. Incompatible with salts of heavy metals, alkaloids, gelatin, albumin, starch, oxidizing substances-e.g., permanganates, chlorates; lime water [Merck].

Опасность

Toxic by ingestion and inhalation. Questionable carcinogen.

Угроза здоровью

Inhalation causes irritation of nose and throat, coughing, and sneezing. Ingestion may cause gastric disturbance. Contact with eyes causes irritation.

Пожароопасность

Special Hazards of Combustion Products: Decomposes at 210° to carbon dioxide and pyrogallol, which can form irritating vapors.

Промышленное использование

Quebracho is the most common tannic acid derivative widely used in flotation. The main phenolic nuclei present in Quebracho are resorcinol/phloroglucinol and catechol/pyrogallol.
Quebracho is commercially available in the following three forms: (a) standard Quebracho, a direct hot-water extract from the heart-wood with adjusted pH (Qu–O), (b) sulfited Quebracho, in which sulfonic acid groups have been introduced (Qu–S) and (c) aminated Quebracho (Qu–A), where amine groups are introduced to ordinary Quebracho, rendering the polymer amphoteric (iso-electric point at pH 7). Each of these types of Quebracho has a different depressing effect.

Профиль безопасности

Poison by intravenous and intraperitoneal routes. Questionable carcinogen with experimental tumorigenic data. When heated to decomposition it emits acrid smoke and irritating fumes.

Синтез

Tannic acid is synthesized by extraction from Nutgalls (Chinese or Turkish), Myrobalans (Terminalia SP.), Oakbark, etc. It is also synthesized by esterification of Glucose with meta-galloylgallic acid.

Экологическая судьба

Tannins and tannic acid occur naturally in plants. Essentially all wood and plant tissue contain tannins. Therefore, biodegradation is expected to be the major environmental fate process for tannic acid.