Cinnamaldehyde

Cinnamaldehyde is the organic compound that gives cinnamon its flavor and odor. This pale yellow viscous liquid occurs naturally in the bark of cinnamon trees and other species of the genus Cinnamomum. The essential oil of cinnamon bark is about 90% cinnamaldehyde.

Structure and synthesis
Cinnamaldehyde was isolated from cinnamon essential oil in 1834 by Dumas and Péligot and synthesized in the laboratory by Chiozza in 1854.

The natural product is trans-cinnamaldehyde. The molecule consists of a phenyl group attached to an unsaturated aldehyde. As such, the molecule can be viewed as a derivative of acrolein. Its color is due to the π → π* transition: increased conjugation in comparison with acrolein shifts this band towards the visible.

Synthesis
Several methods of laboratory synthesis exist, but cinnamaldehyde is most economically obtained from the steam distillation of the oil of cinnamon bark. The compound can be prepared from related compounds like cinnamyl alcohol, (the alcohol form of cinnamaldehyde), but the first synthesis from unrelated compounds was the aldol condensation of benzaldehyde and acetaldehyde.

Biosynthesis
Cinnamaldehyde occurs widely and closely related compounds give rise to lignin. All such compounds are biosynthesized starting from phenylalanine, which undergoes conversion to cinnamoyl ester of coenzyme A.

As a flavorant
The most obvious application for cinnamaldehyde is as flavoring in items like chewing gum, ice cream, candy, and beverages range from 9 to 4900ppm(parts per million) (that is, less than 0.5%). It is also used in some perfumes of natural, sweet, or fruity scents. Almond, apricot, butterscotch, and other aromas may partially employ the compound for their pleasant smells. Cinnamaldehyde can be used as a food adulterant; powdered beechnut husk aromatized with cinnamaldehyde can be marketed as powdered cinnamon.

As an agrichemical
Cinnamaldehyde is also used as a fungicide. Proven effective on over 40 different crops, cinnamaldehyde is typically applied to the root systems of plants. Its low toxicity and well-known properties make it ideal for agriculture. Cinnamaldehyde is an effective insecticide, and its scent is also known to repel animals like cats and dogs. Cinnamaldehyde has recently been recognized as a very effective insecticide for mosquito larvae. As little as 29 ppm (parts per million) of cinnamaldehyde kills half of Aedes aegypti mosquito larvae in 24 hours.

As an antimicrobial
Another use for cinnamaldehyde is as an antimicrobial. Researchers from the University of Illinois at Chicago (who were funded by the Wm. Wrigley Jr. Company) have found that cinnamic aldehyde, when used in Big Red, prevented oral bacterial growth by more than 50 percent. It is especially effective against bacteria living at the back of the tongue, reducing anaerobic bacteria populations by about 43 percent.

As an anti-cancer agent
Recent research documents anti-cancer activity of cinnamaldehyde/cinnamic aldehyde observed in cell culture and animal models of the disease. Proliferation, invasion, and tumor growth were inhibited in a murine A375 model of human melanoma.

Miscellaneous uses
Cinnamaldehyde is also known as a corrosion inhibitor for steel and other ferrous alloys in corrosive fluids. It can be used in combination with additional components such as dispersing agents, solvents and other surfactants.

Derivatives of cinnamaldehyde
Numerous derivatives of cinnamaldehyde are commercially useful. Dihydrocinnamic alcohol (CAS#122-97-4), which occurs naturally but is produced by double hydrogenation of cinnamaldehyde, is used to confer the fragrances of hyacinth and lilac. Cinnamic alcohol (CAS#104-54-1) similarly occurs naturally and has the odor of lilac. Dihydrocinnamaldehyde (CAS#104-53-0) is produced by the selective hydrogenation of the alkene subunit. α-Amyl- and α-hexylcinnamaldehyde are important commercial fragrances, but they are not prepared from cinnamaldehyde.

Toxicology
Cinnamaldehyde is used in agriculture because of its low toxicity. It is however a skin irritant. The level of coumarin detected in 'cinnamon' extracts and powders has concerned the German BfR.