Gallic acid is a trihydroxybenzoic acid found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants.
Gallic acid is found both free and as part of hydrolyzable tannins. The gallic acid groups are usually bonded to form dimers such as ellagic acid. Hydrolysable tannins break down on hydrolysis to give gallic acid and glucose or ellagic acid and glucose, known as gallotannins and ellagitannins respectively.
1.Gallic acid has antibacterial effect and can treat bacillary dysentery. It has astringent, hemostasis and antidiarrheic effects;
2.In food industry, it can be used to prepare preservative propyl gallate;
3.It can be used in the production of mordant dyes and as a developer, etc.;
4.It forms blue-black precipitate with ferric ion, which is the raw material of blue-black ink;
5.It can be combined with vitamin C as a fortified bait to raise fish;
6.It is also used in tanning industry and can also be used as a photographic developer.