Cinnamaldehyde is an organic compound with the formula or . Occurring naturally as predominantly the trans ( E) isomer, it gives cinnamon its Flavoring and odor.
Structure and synthesis
Cinnamaldehyde was isolated from cinnamon essential oil in 1834 by Jean-Baptiste Dumas and Eugène-Melchior Péligot
and synthesized in the laboratory by the Italian chemist Luigi Chiozza in 1854.
Synonyms for Cinnamaldehyde include 3-Phenyl-2-propenal, Cinnamic aldehyde, trans-Cinnamaldehyde, Cinnamal, Cinnamyl aldehyde, Cassia aldehyde, 3-Phenylacrolein, and β-Phenylacrolein.
The natural product is trans-cinnamaldehyde. The molecule consists of a benzene ring attached to an unsaturated aldehyde. Cinnamaldehyde is an α,β-unsaturated carbonyl compound. Its color is due to the π → π* transition: increased conjugation in comparison with acrolein shifts this band towards the visible.
The molecule can be identified by characteristic spectroscopic signals. Infrared spectra show strong absorption bands near 1685 cm-1 (C=O stretch) and 1620 cm-1 (C=C stretch). In the proton nuclear magnetic resonance (1H NMR) spectrum, the aldehydic proton resonates around 9.6 ppm, while aromatic and vinyl protons appear between 6.3 and 7.6 ppm.
Biosynthesis
Cinnamaldehyde is biosynthesized from
phenylalanine.
of
L-phenylalanine into
cinnamic acid is catalyzed by phenylalanine ammonia lyase (PAL).
PAL catalyzes this reaction by a non-oxidative deamination. This deamination relies on the MIO prosthetic group of PAL.
PAL gives rise to
trans-cinnamic acid. In the second step, 4-coumarate–CoA ligase (4CL) converts cinnamic acid to cinnamoyl-CoA by an acid–
thiol ligation.
4CL uses ATP to catalyze the formation of cinnamoyl-CoA.
4CL effects this reaction in two steps.
4CL forms a hydroxycinnamate–AMP anhydride, followed by a nucleophile attack on the carbonyl of the acyl adenylate.
Finally, Cinnamoyl-CoA is reduced by NADPH catalyzed by CCR (cinnamoyl-CoA reductase) to form cinnamaldehyde.
Preparation
Several methods of laboratory synthesis exist. The compound can be prepared from related compounds such as
cinnamyl alcohol. An early synthesis involved the aldol condensation of
benzaldehyde and
acetaldehyde.
[Richmond, H. Preparation of Cinnamaldehyde. US Patent Application 2529186, November 7, 1950.] Cinnamaldehyde can also be obtained from the steam distillation of the oil of cinnamon bark.
Cinnamaldehyde is stable under dry, cool, and dark storage conditions but slowly oxidizes in air and light to form cinnamic acid and related degradation products. It is slightly soluble in water but miscible with organic solvents such as ethanol, ether, and chloroform.
Applications
As a flavorant
The most obvious application for cinnamaldehyde is as
flavoring in
chewing gum,
ice cream,
candy,
e-liquid and
; use levels range from 9 to 4,900 parts per million (ppm) (that is, less than 0.5%). It is also used in some
of natural,
sweet, or
.
Almond,
apricot,
butterscotch, and other
may partially employ the compound for their pleasant smells. Cinnamaldehyde can be used as a
food adulterant; powdered
husk aromatized with cinnamaldehyde can be marketed as powdered
cinnamon.
Some breakfast cereals contain as much as 187 ppm cinnamaldehyde.
As an agrichemical
Cinnamaldehyde has been tested as a safe and effective insecticide against
mosquito .
A concentration of 29 ppm of cinnamaldehyde kills half of
Aedes aegypti mosquito larvae in 24 hours.
Trans-cinnamaldehyde works as a potent
fumigant and practical repellant for adult
.
It also has
antibacterial and
antifungal properties.
Miscellaneous uses
Cinnamaldehyde is a corrosion inhibitor for
steel and other
. It is believed to form a protective film on the metal surface.
In addition to flavor and fragrance applications, cinnamaldehyde is used in small amounts as a natural preservative in cosmetic and personal care formulations. It exhibits mild antimicrobial and antioxidant activity that helps extend product shelf life.
Derivatives
Numerous derivatives of cinnamaldehyde are commercially useful. Dihydrocinnamyl alcohol (3-phenylpropanol) occurs naturally but is produced by double
hydrogenation of cinnamaldehyde. It has the fragrances of hyacinth and lilac.
Cinnamyl alcohol similarly occurs naturally and has the odor of lilac but can be also produced starting from cinnamaldehyde.
Dihydrocinnamaldehyde is produced by the selective hydrogenation of the alkene subunit. α-Amylcinnamaldehyde and α-hexylcinnamaldehyde are important commercial fragrances, but they are not prepared from cinnamaldehyde.
[ Hydrogenation of cinnamaldehyde, if directed to the alkene, gives hydrocinnamaldehyde. Aldol condensation of cinnamaldehyde with acetone forms dicinnamalacetone, which is used as an indicator. Cinnamonitrile can be produced by an elimination reaction of various Oxime derived from cinnamaldehyde.]
Toxicology
Cinnamaldehyde is used in agriculture because of its low toxicity, but it is a skin irritant.
Cinnamaldehyde can contain traces of styrene, which arises during storage or transport. Styrene especially forms in high humidity and high temperatures.
DNA repair
Cinnamaldehyde is a dietary antimutagen that effectively inhibits both induced and spontaneous .
Biological effects
Cinnamaldehyde is a bioactive electrophile that activates the transient receptor potential ankyrin 1 (TRPA1) ion channel, a chemosensory receptor expressed in sensory neurons and in the gastrointestinal tract. TRPA1 detects pungent or irritant compounds such as those found in cinnamon, mustard oil, and clove, producing the characteristic warming or burning sensation associated with these spices.
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