Tannins catechin

FIGURE 11.3 Condensed tannin. Catechin, a flavan-3-ol, is one of the most common building blocks. 

Potentilla erecoa (L.) Rauschel. P. tormentilla (L.) Rauschel. Tannins, catechins, ellagitannins, phlobaphene." Gargle for throat infections, mouthwash for canker sores and infected gums. 

From a chemical standpoint tannins are formed by the polymerization of elementary phenolic molecules according to the nature of these molecules, one can distinguish hydrolyzable tannins (gallics) and condensed tannins (catechins). 

Both marketers of manufactured superfruit products and the public media have exaggerated the potential antioxidant importance of fruit compounds such as polyphenol pigments (anthocyanins, flavonoids, tannins, catechins, xanthones, and many others). These compounds have antioxidant activity in controlled laboratory conditions, but there is no scientifically confirmed evidence that they have antioxidant roles in the human body. 

Theae folium Tea Camellia sinensis (L,) KUN1"ZB Theaceae MD 2.5%-4d% caffeine 0.02%-0.03% theophylline 0.05% theobromine Polyphenols tannins catechin type (10% 20%), dimeric thcaBavins, oligomeric procyanidins flavonoid glycosides Fig. 29,30... 

Tannins Catechin polymers Epicatechin polymers Ellagitannins Proanthocyanidi ns Tannic acids Grape seed/skin, apple juice, strawberries, raspberries, pomegranate, walnuts, peach, blackberry, and plum 118]... 

Gallotannin Chestnut tannin Catechin Wattle tannin... 

Gallic acid Tannic acid Wattle tannin Catechin ... 

Phytochemistry The roots contains tannins (catechins, gallic acid, pyrogallol, and pyrocatechin), carbohydrates, and glycosides (Khalmatov 1964). The aboveground parts contain vitamins C, A, E, B, B, B, B,j, organic acids (malic and oxalic), sugars, fibers, hemiceUulose, pectin, and macroelements (Nuraliev 1989). Roots collected in Uzbekistan contained new phenylbutanoid and stilbene derivatives as well as the known compounds rhododendrol, epi-rhododendrin, lindleyin, torachrysone, etc. (Shikishima et al. 2001). 

Although the vanillin reaction has been widely used to estimate condensed tannins (proanthocyanidins), the reaction is not specific for this kind of compound. Any appropriately substituted flavanol reacts in the assay as does the monomeric unit of condensed tannins, catechin, that reacts with vanillin to yield a red colored adduct. Moreover, the subunits of the polymeric condensed tannins show variable reactivity with vanillin. In this sense, a modified vanillin method has been proposed to estimate the molecular weight on condensed tannins instead of using it with quantitative purposes. 

Flavanols and procyanidins Flavanols, or flavan-3-ols, are synthesized via two routes, with (+) catechins formed from flavan-3,4-diols via leucoanthocyanidin reductase (LAR), and (—) epicatechins from anthocyanidins via anthocyanidin reductase (ANR) (see Fig. 5.4). These flavan-3-ol molecules are then polymerized to condensed tannins (proanthocyanidins or procyanidins), widely varying in the number and nature of their component monomers and linkages (Aron and Kennedy 2008 Deluc and others 2008). It is still not known whether these polymerization reactions happen spontaneously, are enzyme catalyzed, or result from a mixture of both. 

Flavan-3,4-diols FIavan-3,4-diols, also known as leucoanthocyanidins, are not particularly prevalent in the plant kingdom, instead being themselves precursors of flavan-3-ols (catechins), anthocyanidins, and condensed tannins (proanthocyanidins) (see Fig. 5.4). Flavan-3,4-diols are synthesized from dihydroflavonol precursors by the enzyme dihydroflavonol 4-reductase (DFR), through an NADPH-dependent reaction (Anderson and Markham 2006). The substrate binding affinity of DFR is paramount in determining which types of downstream anthocyanins are synthesized, with many fruits and flowers unable to synthesize pelargonidin type anthocyanins, because their particular DFR enzymes cannot accept dihydrokaempferol as a substrate (Anderson and Markham 2006). 

The cacao plant, Theobroma cacao, is the source of chocolate which is well known and highly prized in international commerce. The cacao pods contain beans which are fermented and pressed to provide a brown liquid which is the raw material for chocolate. The press cake is ground and sold as cocoa and it also provides a brown colorant. The pods, beans, shells, husks and stems have also been suggested as colorants. They contain a very complex mixture of acyl acids, leucoanthocyanins, flavonoid polymers, tannins, and catechin-type polymers.33... 

Partial transformation of rust into ferric-tannates was found to occur with the addition of mangrove tannins leading to a low inhibitive behaviour. The mechanism of adsorption of catechin onto the iron surface has been established via theoretical... 

Polyphenols and Tannins Tannic acid Quercetin Catechin Ellagic acid Rutin... 

The platelet hist UIline release assay demonstrated that cotton mill dust extract, cotton bract extract, cotton leaf extract, dialyzed CMD extract, polyphenols, compound 48/80, rutin, trimethylamine HCl, quercetin, catechin, tannic acid, ellagic acid and sodium metasilicate all release histamine directly (48). Thus not only do tannin compounds induce histamine release, but they may also form higher molecular weight polymers and contain components that survive acid hydrolytic conditions (48). Tannins are widely distributed in the plant kingdom. 

Complex phenolics Coumarins, phenolic quinones, lignins, flavonoids, stilbenes, hydrolyzable tannins, condensed (or catechin) tannins, phenolic lipids... 

Condensed or catechin tannins (catechol tannins. Fig. 11.3) are the most common tannins in vascular plants, occurring in three quarters of gym-nosperms and over half of the angiosperms. They are unbranched, linear polymers of flavonoid compounds (flavan-3-ols), linked through acid-labile carbon-carbon bonds. Condensed tannins may protect plant cell walls against microbial attack and so may affect microbial fermentation of plant cell walls in herbivores. 

Microbial Degradation of Catechin. Since (+) catechin is a possible biodegradation product from condensed tannins, its utilization and bioconversion have been extensively examined by several research groups using fungi, bacteria and yeasts. 

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