Home > Tannins
Tannins are astringent , bitter-tasting plant polyphenols that bind and precipitate proteins. The term tannin (from the Celtic word for oak) refers to the source of tannins used to convert animal skin into leather; however, the term is applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with proteins and other macromolecules. Tannins have molecular weights ranging from 500 to over 20,000.Tannins are usually divided into hydrolyzable tannins and condensed tannins (proanthocyanidins). At the center of a hydrolyzable tannin molecule, there is a polyol carbohydrate (usually D-glucose). 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). Hydrolyzable tannins are hydrolyzed by weak acids or weak bases to produce carbohydrate and phenolic acids. Condensed tannins, also known as proanthocyanidins, are polymers of 2 to 50 (or more) flavonoid units that are joined by carbon-carbon bonds, which are not susceptible to being cleaved by hydrolysis. While hydrolyzable tannins and most condensed tannins are water soluble, some very large condensed tannins are insoluble.
Examples of gallotannins are the esters of tannic acid (C76H52O46) with glucose, found in the leaves and bark of many plantGreen algae land plants (embryophytes non-vascular embryophytes Hepatophyta liverworts Anthocerophyta hornworts Bryophyta mosses vascular plants (tracheophytes seedless vascular plants Lycopodiophyta clubmosses Equisetophyta horsetails Pteridophyta "true" species.
1 Tea
The teaThis article is about the beverage. For alternative meanings, see tea (disambiguation). Tang Dynasty ( 618- 907). Tea is a caffeinated beverage, an infusion made by steeping the dried leaves or buds of the shrub Camellia sinensis in hot water. In addition plant (Camellia sinensis) is an example of a plant with a naturally high tannin content, though in the case of green tea the leaf does not release its tannin into the infusion. Tannins have a calming effect on the humanHuman beings are defined variously in biological, spiritual, and cultural terms, or in combinations thereof. Biologically, they are classified as Homo sapiens ( Latin for knowing man , a primate species of mammal with a highly developed brain. In spiritua central nervous systemThe human central nervous system consists of the brain and spinal cord. These lie in the midline of the body and are associated with the skull and vertebrae respectively. see Nervous System) The central nervous system along with the peripheral nervous sys, countering the stimulating effectA stimulant is a drug which increases the activity of the sympathetic nervous system and produces a sense of euphoria or awakeness. Stimulants can be used as recreational drugs, or therapeutically to increase alertness; they are also used and sometimes ab of the caffeineCaffeine is an alkaloid found naturally in such foods as coffee beans, tea, kola nuts, Yerba mate, guarana, and (in small amounts) cacao beans. It is added to some soft drinks such as colas and Mountain Dew. Caffeine has a characteristic intensely bitter in tea. New varieties of tea have been specifically bred for a lower tannin content. If ingested in excessive quantities, tannins inhibit the absorption of mineralMinerals are natural compounds formed through geological processes. The term "mineral" encompasses not only the material's chemical composition but also the mineral structures. Minerals range in composition from pure elements and simple salts to very comps such as ironThis article is about metallic iron. For the ironing device, see ironing manganese iron cobalt Fe Ru Full table General Name, Symbol, Number iron, Fe, 26 Chemical series transition metal Group, Period, Block 8 (VIIIB), 4 , d Density, Hardness 7874 kg/m3, into the body. This is because tannins are metal ion chelators, and tannin-chelated metal ions are not bioavailable.
