Catechins distribution

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. 

Catechins are widely distributed in plants however, they are rich only in tea leaves, where catechins may constitute up to 25% of dry leaf weight. Catechins of green tea include the flavanols epicatechin, epigallocatechin, and their gallate esters (Table 14). 

An alternative colorimetric method relies on the reaction with vanillin under acidic conditions. A 2-mL aliquot of a freshly prepared solution of vanillin (1 g/100 mL) in 70% sulfuric acid is added to 1 mL of aqueous plant extract. The mixture is incubated in a 20°C-waterbath and after exactly 15 min. the absorbance at 500 nm read. The concentration of proanthocyanidins is expressed as (+)-catechin equivalents (used for the standard curve). This assay is specific for flavonols. As a consequence, when using this assay to determine the concentration of condensed tannins, widely distributed monomeric flavonols, such as catechin (1.39) and epicatechin (1.90), can interfere (Hagerman and Butler, 1989). 

Each compound was distributed among 3-4 individual cells. Since the COX inhibitory activity of catechins and flavonoids are well known, the conclusion from the dereplication process is that these active fractions are not worth pursuing. 

Although flavanols, also called catechins, seem to be widely distributed in plants, they are rich only in tea leaves, where catechins may contribute up to 30% of dry leaf weight. The antioxidative and antitumor properties of green and black teas and their tea polyphenols are extensively studied. It seems that tea polyphenols are important not only for plants but also for humans. Therefore, this brief review will discuss the current data with a particular emphasis on the effects of tea polyphenols on the cellular oxidative stress and cancer chemopreventive properties. The action mechanisms of several phytopolyphenols on cancer chemoprevention will be elaborated. 

There are discordant reports regarding the distribution of the molecular weights (MW) of proanthocyanidins in the seeds. Nevertheless, it has been reported that their mean degree of polymerization (mDP) is lower than 10 and that they are mainly constituted of (+)-catechin and (—)-epicatechin with a minor extent of (—)-epicatechin gallate. (+)-Catechin, (—)-epicatechin and (—)-epicatechin gallate are the terminal monomers (Kennedy and Jones, 2001 Downey et al., 2003 Pastor del Rio and Kennedy, 2006) (—)-epigallocatechin is absent in the seed proanthocyanidins. 

It is well known that tea contains catechins besides caffeine. Although catechins are widely distributed in the plant kingdom, the catechin monomers in many plants coexist with larger amounts of dimeric to polymeric proanthocyanidins, which are comprised of catechin units connected by C-C bonds. However, the polyphenol composition of C. sinensis is unique, and mainly comprised of four monomeric catechins—(-)-epicatechin (1), (-)-epigallocatechin (2) and their galloyl esters. 

It is very important to know the bioavailability and biotransformation of tea catechins in humans because the pharmacokinetics, absorption, distribution, metabolism, and excretion of green tea determine its potential bioactivities in disease prevention in... 

Bioavailability of tea catechins in tissues may be much more important than that in plasma, but little published data are available on tissue distribution of catechins in humans after tea consumption, even in animals. The nature of tissue metabolites... 

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