Origin Gallic acid

Gallic acid is present in tea leaf and is a known reactant during the complex enzymatic and organochemical reactions that occur when tea components are oxidized.51 The gallic and quinic acids originate via the shikimate/arogenate pathway. The key enzymes in shikimic acid biosyn-... 

Singleton and Esau (I) reviewed the methods for phenol analysis of wine. They pointed out that study would be greatly advanced if one could determine the total content of phenolic substances and express it in such a way that analysis of subclasses of phenols could be related to the original total and a balance sheet could be obtained. One could then say, for example, this wine has a total phenolic content of 1200 mg/liter calculated as gallic acid, and of that total, cinnamic acid derivatives account for 200 mg/liter, anthocyanins for 300 mg/liter, other small flavonoids for 200 mg/liter, and condensed tannins complete the total with 500 mg/liter of gallic acid equivalent. To accomplish this, the total phenol analysis not only must meet ordinary criteria of reproducibility and precision, but it also must be based on chemical relationships such that fractions determined separately can be converted to units of the total. Of course when clearcut fractionation can be accomplished by... 

Manufacture and Synthesis. The commercial manufacturing process is based on Scheele s original procedure starting with crude gallic acid,... 

D-Gala-L-manno-heptose, I, 9 V, 10 D-Gala-L-manno-heptose, 7-desoxy-, I, 31 D-Gala-L-manno-heptose oxime, hepta-acetate, IV, 122, 125, 150 D-Gala-D-manno-nonitoI, I, 31 Galaoctose, I, 8 origin of name, III, 12 Gallic acid, III, 75... 

Vanhoenacker et al. 2001). Gallic acid is one of the HBA with the highest concentrations in wine. It not only originates from the grape itself but is also formed by hydrolysis of hydrolyzable and condensed tannins, i.e. the gallic acid esters of flavan-3-ols. 

The hydrolysable ones have a structure of polyesters with two essential constituents — saccharide and phenolcarboxylic acid. Under the effect of hydrolytic agents (acids, enzymes, alkalies) they split into the original components. Thus, gallotannines provide — in addition to the sucrose component — also gallic acid, and elagitannines provide hexahydroxydiphenyl... 

Hydrolyzable tannins are not naturally found in grapes. On the other hand, they are the main commercial tannins legally authorized as wine additives. Ellagic acid in wine originates either from wooden containers or from the addition of enological tannins. On the other hand, gallic acid from the skins and seeds is always present in wine. 

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