Catechin, gallic acid ester

Flavanols/Procyanidins Catechin, epicatechin, and their gallic acid esters Apples, grapes, plums, pears, mangoes, okra, peaches, Swiss chard, berry fruits and vegetables in general,... 

Catechins (1.41) can also be found as gallic acid esters that are esterified at the 3 hydroxyl group. Note the difference between the gallic acid ester of catechin (1.41) and gallocatechin (1.40). 

Building blocks Gallic acid, galloyl ester, ester-linked with glucose Flavanoid units (Procyanidins), catechin... 

In fermenting juice, the gallocatechins are oxidized before the catechins and eptcatechins are attacked. In the earlier stages of fermentation gallic acid shows a marked increase, presumably by liberation from ester combination. Similar changes are observed in fermenting tea leaf, in which, as the catechins disappear, more complex substances are formed which are probably condensation products (Harrison and Roberts, 1939). 

It was reported that esterification of (—)-epicatechin and procyanidin B2 by gallic acid can occur and that these gallate esters are only found in the grape seed extract. Grape seed extract contains oligomer procyanidins made up of dimers or trimers of (+)-catechin and (—)-epicatechin.4-6 The procyanidin dimers are comprised of procyanidins Bl, B2, B3, B4, B5, B6, B7, and B8. There are six procyanidin trimers which include procyanidins Cl and C2. 

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