MOLECULE

trans-Cinnamic acid

Trans-cinnamic acid, also known as (e)-cinnamic acid or phenylacrylic acid, belongs to the class of organic compounds known as cinnamic acids. These are organic aromatic compounds containing a benzene and a carboxylic acid group forming 3-phenylprop-2-enoic acid. Cinnamic acid can exist in both the cis and trans form, with the trans-form being most common. Trans-cinnamic acid is a weakly acidic compound (based on its pKa). It is a white crystalline compound that is slightly soluble in water, and freely soluble in many organic solvents. Trans-cinnamic acid occurs naturally in a number of plants. It is a sweet, balsam, or cinnamon tasting compound. Trans-cinnamic acid is characterized by a honey-like odor. Trans-cinnamic acid is found in a number of foods with the highest concentration found in chinese cinnamons (cinnamon bark), olives, and lingonberries and in a lower concentration in redcurrants, red raspberries, and corianders. Trans-cinnamic acid has also been detected, but not quantified in common oregano, pepper (spice), fennels, pomegranates, and european cranberries. Trans-cinnamic acid has also been shown to be a microbial metabolite as it is produced by microbes belonging to the Alcaligenes, Brevibacterium, Cellulomonas, and Pseudomonas families (PMID: 16349793). In plants, cinnamic acid is a central intermediate in the biosynthesis of myriad natural products include lignols (precursors to lignin and lignocellulose), flavonoids, isoflavonoids, coumarins, aurones, stilbenes, catechin, and phenylpropanoids. Its biosynthesis involves the action of the enzyme phenylalanine ammonia-lyase (PAL) on phenylalanine (PMID:20035037). Cinnamic acid is used in flavorings, the production of synthetic indigo, and certain pharmaceuticals. A major use of trans-cinnamic acid is as a precursor to produce methyl cinnamate, ethyl cinnamate, and benzyl cinnamate for the perfume industry.