Wednesday, March 28, 2012

Coumaric Acid

Coumaric acid is a hydroxycinnamic acid, an organic compound that is a hydroxy derivative of cinnamic acid. There are three isomers, o-coumaric acid, m-coumaric acid, and p-coumaric acid, that differ by the position of the hydroxy substitution of the phenyl group. p-Coumaric acid is the most abundant isomer of the three in nature.
Together with sinapyl alcohol and coniferyl alcohols, p-coumaric acid is a major component of lignocellulose. It is biosynthesized from cinnamic acid by the action of the P450-dependent enzyme 4-cinnamic acid hydroxylase.

p-Coumaric acid can be found in a wide variety of edible plants such as peanuts, tomatoes, carrots, and garlic. It is a crystalline solid that is slightly soluble in water, but well soluble in ethanol and diethy ether.  It is also found in wine and vinegar.

p-Coumaric acid is the precursor of 4-ethylphenol produced by the yeast Brettanomyces in wine. The yeast converts this to 4-vinylphenol via the enzyme cinnemate decarboxylace. 4-Vinylphenol is further reduced to 4-ethylphenol by the enzyme vinyl phenol reductase. Coumaric acid is sometimes added to microbiological media, enabling the positive identification of Brettanomyces by smell.


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