What is cinnamic acid used for?

Cinnamic acid exists as trans and cis isomers, but the trans form is the one most often found in nature and is the article of commerce. It is obtained from cinnamon bark and balsam resins such as storax. It was first isolated in 1872 by F. Beilstein (of Handbook of Organic Chemistry fame) and A. Kuhlberg. It is synthesized by the Perkin reaction between Ac2O and PhCHO.

Trans-Cinnamic acid is used in the manufacture of flavors, dyes, and pharmaceuticals; but its major use is for the production of its methyl, ethyl, and benzyl esters. These esters are important components of perfumes. The acid is also a precursor to the sweetener aspartame.

Cinnamic acid derivatives are widely used in cosmetics and possess various functions. This group of compounds includes both naturally occurring and synthetic substances. On the basis of the Cosmetic Ingredient Database (CosIng) and available literature, this review summarizes their functions in cosmetics, including their physicochemical and biological properties as well as reported adverse effects.

A perfuming function is typical of many derivatives of cinnamaldehyde, cinnamyl alcohol, dihydrocinnamyl alcohol and cinnamic acid itself; these substances are commonly used in cosmetics all over the world. Some of them show allergic and photoallergic potential, resulting in restrictions in maximum concentrations and/or a requirement to indicate the presence of some substances in the list of ingredients when their concentrations exceed certain fixed values in a cosmetic product.

Another important function of cinnamic acid derivatives in cosmetics is UV protection. Ester derivatives such as ethylhexyl methoxycinnamate (octinoxate), isoamyl p-methoxycinnamte (amiloxiate), octocrylene and cinoxate are used in cosmetics all over the world as UV filters. However, their maximum concentrations in cosmetic products are restricted due to their adverse effects, which include contact and a photocontact allergies, phototoxic contact dermatitis, contact dermatitis, estrogenic modulation and generation of reactive oxygen species.

Other rarely utilized functions of cinnamic acid derivatives are as an antioxidant, in skin conditioning, hair conditioning, as a tonic and in antimicrobial activities. Moreover, some currently investigated natural and synthetic derivatives of cinnamic acid have shown skin lightening and anti-ageing properties. Some of them may become new cosmetic ingredients in the future. In particular, 4-hydroxycinnamic acid, which is currently indexed as a skin-conditioning cosmetics ingredient, has been widely tested in vitro and in vivo as a new drug candidate for the treatment of hyperpigmentation.

The medicinal applications in form of derivatives make cinnamic acid highly important. The developing countries like India and Brazil form the major market for cinnamic acid owing to the increase in number of patients suffering from tuberculosis and malaria especially in rural areas. Thus the demand for cinnamic acid would boost up in these countries. Cinnamic acid market is also driven by its application in cosmetic industry. There is a huge demand for skin care products across developed countries like the U.S., Russia and other European market.