Tannic acid

Tannic acid is a plant-derived mixture of hydrolysable polyphenols that binds proteins and other molecules. It is used in leather tanning, inks, dyes, and some medicines.

Hydrolysable tannins: Plant polyphenols that break down through hydrolysis into sugars and phenolic acids. Tannic acid belongs to this broad class, whose members share ester-linked structures.
Vegetable tanning: A leather-making process that uses plant tannins to stabilize animal hides. Tannic acid and related tannins bind collagen during this tanning process.
Galls: Abnormal plant growths induced by organisms such as insects, mites, fungi, or bacteria. Oak galls were a traditional source of tannin-rich material used to prepare tannic acid.
Tannin: A diverse group of plant polyphenols that bind proteins and other macromolecules. Tannic acid is one particular tannin preparation, not a name for all tannins.
Protein precipitation: The formation of insoluble aggregates when proteins bind and separate from solution. Tannic acid binds multiple sites on proteins, often making them precipitate.
Dye: A colored substance that imparts color to a material through chemical or physical interaction. Tannic acid can act as a mordant that helps dyes attach to fibers.
Oak gall: A gall on an oak tree, often induced by gall wasps and rich in tannins. Oak galls supplied the tannins used in traditional inks and early tannic-acid preparations.
Condensed tannin: A class of tannins built from flavonoid units linked into oligomers or polymers. Unlike hydrolysable tannic acid, condensed tannins do not readily yield gallic acid by hydrolysis.
Hydrogen bond: An attraction involving a hydrogen atom bonded to an electronegative atom and another electronegative atom. Hydrogen bonding helps tannic acid associate with protein surfaces.
Mordant: A substance that helps a dye bind to a material, often by forming a coordination complex. Tannic acid improves the uptake of some dyes on textiles.

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Ellagic acidCompared with: Unlike ellagic acid, it is a larger, heterogeneous tannin preparation.