Syringic acid

Syringic acid is a naturally occurring phenolic compound and dimethoxybenzene that is commonly found as a plant metabolite.

Natural occurrence
Syringic acid can be found in several plants including Ardisia elliptica and Schumannianthus dichotomus. It is biosynthesized by the shikimic acid pathway in plants.

Synthesis
Syringic acid can be prepared by selectively hydrolyzing (demethylating) eudesmic acid with 20% sulfuric acid.

Presence in food
Syringic acid can be found in several fruits including olives, dates, spices, pumpkin, grapes, acai palm, honey, red wine, among others. Its presence in the ancient Egyptian drink shedeh could confirm it was made out of grape, as syringic acid is released by the breakdown of the compound malvidin, also found in red wine. It is also found in vinegar.

Applications
Various studies have found syringic acid to have potentially useful properties such as anti-oxidant, anti-microbial, anti-inflammation, anti-cancer, and anti-diabetic.

Syringic acid can be enzymatically polymerized. Laccase and peroxidase induced the polymerization of syringic acid to give a poly(1,4-phenylene oxide) bearing a carboxylic acid at one end and a phenolic hydroxyl group at the other.