Trans Stilbene

Cinnamic acid is an organic compound with the formula C6H5CH=CHCOOH. It is a white crystalline compound that is slightly soluble in water, and freely soluble in many organic solvents. Classified as an unsaturated carboxylic acid, it occurs naturally in a number of plants. It exists as both a cis and a trans isomer, although the latter is more common.

Cinnamic acid is a central intermediate in the biosynthesis of myriad natural products include lignolsto lignin and lignocellulose, flavonoids, isoflavonoids, coumarins, aurones, stilbenes, catechin, and phenylpropanoids. Its biosynthesis is performed by action of the enzyme phenylalanine ammonia-lyase (PAL) on phenylalanine.

Cinnamic acid is a precursor for the synthesis of a huge number of plant substances, including lignin, tannins, flavonoids, pigments, many of the flavor components of spices, and various alkaloids, such as morphine and colchicine.