Hydroxycinnamic acids (hydroxycinnamates) are a class of aromatic acids or phenylpropanoids having a C6C3 skeleton. These compounds are hydroxy derivatives of cinnamic acid. Among these esters of interesting natural compounds are found: Caffeic, Cichoric, Cinnamic, Chlorogenic, Diferulic, Coumaric, Ferulic, Sinapinic, sinapic acid