Catechins structure

Anthocyanins and anthocyanidins, compounds present with high structural diversity in fruits and wines, showed a pattern as antioxidants different from that of the tea catechins with respect to the effect of substituents. In a liposomal model system induced peroxidation was inhibited increasingly by anthocyanins/ anthocyanidins with an increasing number of hydroxyl groups in the B-ring (Fig. 16.6), while the opposite was seen for the catechins (Seeram and Nair, 2002). For anthocyanidins, the presence of a 3-hydroxy group is important... 

GUO Q, ZHAO B, SHEW s, Hou J, HU J and xiN w (1999) ESR study of the structure -antioxidant activity relationship of tea catechins and their epimers, Biochem Biophys Acta, 1427, 13-23. 

SEERAM N P and NAIR M G (2002) Inhibition of lipid peroxidation and structure-activity-related studies of the dietary constituents autocyanins, autocyanidins, and catechins, JAgric Food Chem, 50, 5308-12. 

Duenas, M., et al., UV-visible spectroscopic investigation of the 8,8-methylmethine catechin-malvidin-3-glucoside pigments in aqueous solutions structural transformations and molecular complexations with chlorogenic acid, J. Agric. Food. Chem., 54, 189, 2006. 

The occurrence in some plants of secondary metabolites characterized by an 0-heterocyclic structure and exhibiting antimicrobial properties is a well-known phenomenon [2,8-10]. Among them, catechins and proanthocyanidins are two classes of compounds exhibiting antimicrobial properties towards both prokaryotic and eukaryotic microorganisms. Yet, despite the large number of studies published so far, the real potentialities and limitations given by the use of this class of molecules as antiviral or antimicrobial (antibacterial, antimycotic, antiprotozoal) agents have not been critically evaluated. The present chapter represents an overview of the re-... 

First, the qualitative and quantitative variability of the amount of catechins and proanthocyanidins present in plant extracts used for different studies is probably the most significant. This might be due to the use of different procedures of extraction, quantification and structural elucidation. In most cases, even the lack of rigorous phytochemical characterization and quantification of active compoimd(s) constitutes a severe limitation on the rehabihty of the results. The lack of commercially available pure standards (particularly for some proanthocyanidins) represents an additional problem that has so far hampered the execution of rigorous SAR studies. This hmitation means that although a munber of in vitro or in vivo studies have been carried out by using more or less pure standards of catechins or with plant extracts containing both catechins and proanthocyanidins, only a handful of authors have... 

As indicated in Table 2, the polyphenols constitute the most abundant group of compounds in tea leaf. Of these, the epi- form of the catechin group of fiavanois predominate. Their structure is shown in Figure 2. 

The initial oxidation of the flavanol components of fresh leaf to quinone structures through the mediation of tea polyphenol oxidase is the essential driving force in the production of black tea. While each of the catechins is oxidizable by this route, epigallocatechin and its galloyl ester are preferentially oxidized.68 Subsequent reactions of the flavonoid substances are largely nonenzymic. 

Takino, Y., Reddish orange pigments of black tea structure and oxidative formation from catechins. JARQ, 12 94, 1978. 

Flavonoids are a complex group of polyphenolic compounds with a basic C6-C3-C6 structure that can be divided in different groups flavonols, flavones, flavanols (or flavan-3-ols), flavanones, anthocyanidins, and isoflavones. More than 6,000 flavonoids are known the most widespread are flavonols, such as quercetin flavones, such as lu-teolin and flavanols (flavan-3-ols), such as catechin. Anthocyanidins are also bioactive flavonoids they are water-soluble vegetable pigments found especially in berries and other red-blue fruits and vegetables. 

Fig. 2.102. Structures of all the compounds found in fraction A (a) anthocyanins (b) A-type vitisins (c) pyranoanthocyanins originated by reaction between anthocyanins and vynilphenol, vynilcatechol or vynilguaiacol (d) pyranoanthocyanins originated by reaction between anthocyanins and vynil(epi)catechin. Reprinted with permission from C. Alcalde-Eon et al. [236],...

Fig. 3.1 Structures of (a) catechin, (b) epicatechin, (c) epicatechin gallate, (d) general structure of PAs, and (e) procyanidin dimer...

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