Aleppo gall nuts(Alep) are hard nutlike galls that form on the Aleppo oak (Quercus infectoria) in response to the developing larva of a gall wasp. They are used as a source of gallic acid and tannin.
Tannic acids are organic compounds that contain a 3,4,5-trihydroxybenzoic acid moiety. Gallic acid exists as a solid,slightly soluble (in water),and a weakly acidic compound (based on its pKa).
Have been harvested for thousands of years as a concentrated source of tannins for use in high-quality inks,in medicine,etc.