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Larrea tridentata
Published in Cristobal N. Aguilar, Suresh C. Ameta, A. K. Haghi, Green Chemistry and Biodiversity, 2019
Janeth Ventura-Sobrevilla, Gerardo Gutiérrez-Sánchez, Carl Bergmann, Parastoo Azadi, Daniel Boone-Villa, Raúl Rodriguez-Herrera, Cristóbal N. Aguilar
Tannins are present in fruits and vegetables and they are considered secondary plant metabolites. Tannins are the second most abundant group of plant phenolic compounds just after lignins (Bhat et al., 1998). The medicinal properties of tannins, such as antimicrobial, antiviral, antitumor, anticarcinogen, antioxidant, and anti-inflammatory have been recently reviewed and highlighted (Ascacio-Valdés et al., 2011; Viuda-Martos et al., 2010; Isemura et al., 1999). On the basis of their structural characteristics, it is possible to divide them into four major groups: gallotannins, ellagitannins, complex tannins, and condensed tannins (Ascacio-Valdes et al., 2011). Gallotannins and ellagitannins have a polyol core, commonly sugar, esterified by galloyl units, whereas in complex tannins catechin unit is bound glycosidically to gallotannin or ellagitannin units (Ascacio-valdés et al., 2011; Khanbabaee and Ree, 2001).
Vegetable tannin composition and its association with the leather tanning effect
Published in Chemical Engineering Communications, 2020
Priscila Auad, Franciela Spier, Mariliz Gutterres
The minimum size and reactivity required to have a tanning capacity can be achieved in a number of ways, and the most common way in nature seems to be the binding of esters or gallic acids to the central part of a carbohydrate. These molecules are easily hydrolyzed with acids, bases, or enzymes and are therefore called hydrolyzable tannins (Grasel et al., 2016a). Despite their non-polymer origin, this family of tannins can form complex structures (Belgacem and Gandini, 2008). The hydrolyzable tannins are chemically divided into gallotannins and ellagic tannins. Galotannins are glucose and polyesters of gallic acid commonly found in nature, and they release gallic acid when hydrolyzed. Meanwhile, ellagic tannins are characterized by a glucose center esterified with at least one unit of hexahydroxydiphenyl acid, which is formed by the oxidative coupling of two units of gallic acid (Belgacem and Gandini, 2008). On the other hand, other polyphenolic mixtures present in plants do not undergo hydrolysis, with these being called condensed tannins or proanthocyanidins. They are oligomers or polymers of the basic structure of flavan-3-ol (Koleckar et al., 2008).
Identification of phenolic compounds and antioxidant activity of guava dehydrated by different drying methods
Published in Drying Technology, 2020
Xuan Liu, Xu Yan, Jinfeng Bi, Xinye Wu, Jianing Liu, Mo Zhou
The hydrolyzable tannins are known as gallotannins and ellagitannins. Gallotannins are composed of glucose molecules with one or multiple galloyl groups, whereas ellagitannins are polymers of hexahydroxydiphenoyl (HHDP) group attached to glucose cores. Gallotannins and ellagitannins are superimposed via connection of esterified galloyl and HHDP to form diversified macromolecular phenols.[17]