Gallotannins and ellagitannins

Simple phenolics and their derivatives (benzoic, gallic, ellagic, gallotannins and ellagitannins), flavonoids and condensed tannins... 

Niemetz R, Gross GG (2005), Enzymology of gallotannin and ellagitannin biosynthesis , Phytochemistry, 66, 2001-2011. 

Little knowledge also exists on the mechanisms involved in the biosynthesis of the characteristic structures of gallotannins and ellagitannins, as will be briefly discussed below. 

Hartzfeld, P.W. Forkner, R. Hunter, M.D. Hagerman, A.E. 2002. Determination of hydrolyzable taimins (gallotannins and ellagitannins) after reaction with potassium iodate. J. Agric. Food Chem. 50 1785-1790. 

This fruit contains hydrolysable tannins (both gallotannins and ellagitannins), and ellagic acid isomers (Fig. 5). The pulp contains 0.43-4.64 mg ellagic acid per g d.w. (dry weight) while the achenes contain 1.37-21.65 mg/g [29]. In juice, ellagic acid content ranges from 22 to 45.5 mg/L [30]. 

Depending on their structures, tannins are defined as hydrolyzable (gallotannins and ellagitannins) or condensed (monomers, dimers, oligomers, and polymers of flavan-3-ols). Condensed tannins are also known as proanthocyanidins [3,47]. Proanthocyanidins can be divided into propelargonidins, based on the hydroxylation pattern of the A- and B-rings [3]. Of these, procyanidins constitute the most common subclass of flavonoids in foods, and prodelphinidins and propelargonidins are also present [48,49]. 

Several hydroxylated and methoxylated derivatives of benzoic acid (phenyl carboxylic acid) occur in nature (Table 52). They are the mother substances of reduced compounds (derivatives of benzaldehyde and benzylalcohol), of de-carboxylated products (hydroquinone-derived compounds), but also of more complex substances, e.g., the gallotannins and ellagitannins. 

Mingshu L, Kai Y, Qiang H, Dongying J. Biodegradation of gallotannins and ellagitannins. / Basic Microbiol. 2006 46 68-84. 

Fig. 64.1 General biosynthetic pathway of hydrolyzable tannins (i.e., gallotannin and ellagitannins) as well as Okuda s and Haslam s classificatirai...

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