Wikipedia
Digallic acid
Digallic acid is a polyphenolic compound found in Pistacia lentiscus. Digallic acid is also present in the molecule of tannic acid. Digalloyl esters involve either -meta or -para depside bonds.
Tannase is an enzyme that uses digallate to produce gallic acid. This enzyme can also be used to produce digallic acid from gallotannins.