Molecular formula: C 76 H 52 O 46
[English name] Acidum Tannicum
[Alias] ellagic acid, tannin, tannic acid, tannin.
[Source] is a kind of ellagic acid obtained from Pentelic acid.
[Properties] yellow or light brown light non-crystalline powder or scales; has a peculiar odor, taste very astringent. Soluble in water and ethanol, soluble in glycerol, insoluble in ether, chloroform or benzene. Its aqueous solution and iron salt solution meet blue-black, add sodium sulfite can delay the discoloration.
[Role and use] It is an astringent, can precipitate proteins, and can form insoluble complexes with alkaloids, glycosides and heavy metals.
Mung beans, when put in an iron pot and boiled will turn black; apples, pears cut with an iron knife, the surface will also turn black. This is because green beans, apples, pears and many fruits in the cells, all contain ellagic acid. Ellagic acid can combine with iron to produce black iron tannate. When green beans are cooked in an iron pot, some black iron ellagate is produced.
In industry, ellagic acid is used extensively in tanning leather and in the manufacture of blue ink.
Tea also contains ellagic acid, also known as tannins or tea tannins. It is the most important substance that is responsible for the harmful effects of strong tea.