Cinnamaldehyde is an
organic compound with the formula or C₆H₅CH=CHCHO. Occurring naturally as predominantly the
trans (E) isomer, it gives
cinnamon its
flavor and
odor.[1] It is a
phenylpropanoid that is naturally synthesized by the
shikimate pathway.[2] This pale yellow,
viscous liquid occurs in the
bark of cinnamon
trees and other species of the
genusCinnamomum. The
essential oil of cinnamon bark is about 90% cinnamaldehyde.[3] Cinnamaldehyde decomposes to
styrene because of oxidation as a result of bad storage or transport conditions. Styrene especially forms in high humidity and high temperatures. This is the reason why
cinnamon contains small amounts of styrene.[4]
The natural product is trans-cinnamaldehyde. The molecule consists of a benzene ring 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.[7]
Biosynthesis
Cinnamaldehyde occurs widely, and closely related compounds give rise to
lignin. All such compounds are biosynthesized starting from
phenylalanine, which undergoes conversion.[8]
The biosynthesis of cinnamaldehyde begins with
deamination of L-phenylalanine into
cinnamic acid by the action of
phenylalanine ammonia lyase (PAL).[9][10] PAL catalyzes this reaction by a non-oxidative deamination. This deamination relies on the MIO prosthetic group of PAL.[11] 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.[9] 4CL uses ATP to catalyze the formation of cinnamoyl-CoA.[12] 4CL effects this reaction in two steps.[13] 4CL forms a hydroxycinnamate–AMP anhydride, followed by a nucleophile attack on the carbonyl of the acyl adenylate.[14] Finally, Cinnamoyl-CoA is reduced by NADPH catalyzed by CCR (cinnamoyl-CoA reductase) to form cinnamaldehyde.[9][15]
Preparation
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 such as
cinnamyl alcohol, (the
alcohol form of cinnamaldehyde), but the first synthesis from unrelated compounds was the
aldol condensation of
benzaldehyde and
acetaldehyde; this process was patented by Henry Richmond on November 7, 1950.[16]
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.[25] 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.[17] Hydrogenation of cinnamaldehyde, if directed to the alkene, gives
hydrocinnamaldehyde.
Toxicology
Cinnamaldehyde is used in agriculture because of its low toxicity, but it is a skin irritant.[26] Cinnamaldehyde may cause allergic contact stomatitis in sensitised individuals, however allergy to the compound is believed to be uncommon.[27]
DNA repair
Cinnamaldehyde is a dietary
antimutagen that effectively inhibits both induced and spontaneous
mutations.[28] Experimental evidence indicates that cinnamaldehyde induces a type of
DNA damage in the bacterium Escherichia coli and in human cells that elicits
recombinational DNA repair that then reduces spontaneous mutations.[28][29]
In mice,
X-ray induced
chromosome aberrations were reduced when cinnamaldehyde was given orally to the mice after X-ray irradiation,[30] perhaps due to cinnamaldehyde stimulated
DNA repair.
References
^"Cinnamon". Transport Information Service. Gesamtverband der Deutschen Versicherungswirtschaft e.V. Retrieved 2007-10-23.
^Gutzeit, Herwig (2014). Plant Natural Products: Synthesis, Biological Functions and Practical Applications. Wiley. pp. 19–21.
ISBN978-3-527-33230-4.
^Inuzuka, Kozo (1961). "π Electronic structure of cinnamaldehyde". Bulletin of the Chemical Society of Japan. 34 (11): 1557–60.
doi:
10.1246/bcsj.34.1557.
^Kong, Jian-Qiang (2015-07-20). "Phenylalanine ammonia-lyase, a key component used for phenylpropanoids production by metabolic engineering". RSC Advances. 5 (77): 62587–62603.
Bibcode:
2015RSCAd...562587K.
doi:
10.1039/C5RA08196C.
ISSN2046-2069.
^Beuerle, Till; Pichersky, Eran (2002-03-15). "Enzymatic Synthesis and Purification of Aromatic Coenzyme A Esters". Analytical Biochemistry. 302 (2): 305–312.
doi:
10.1006/abio.2001.5574.
PMID11878812.
^Friedman, M.; Kozuekue, N.; Harden, L. A. (2000). "Cinnamaldehyde content in foods determined by gas chromatography-mass spectrometry". Journal of Agricultural and Food Chemistry. 48 (11): 5702–5709.
doi:
10.1021/jf000585g.
PMID11087542.
^Ma, W.-B.; Feng, J.-T.; Jiang, Z.-L.; Zhang, X. (2014). "Fumigant Activity of 6 Selected Essential Oil Compounds and Combined Effect of Methyl Salicylate And trans-Cinnamaldehyde Against Culex pipiens pallens". Journal of the American Mosquito Control Association. 30 (3): 199–203.
doi:
10.2987/14-6412R.1.
PMID25843095.
S2CID36621630.
^Olsen, R. V.; Andersen, H. H.; Møller, H. G.; Eskelund, P. W.; Arendt-Nielsen, L (2014). "Somatosensory and vasomotor manifestations of individual and combined stimulation of TRPM8 and TRPA1 using topical L-menthol and trans-cinnamaldehyde in healthy volunteers". European Journal of Pain. 18 (9): 1333–42.
doi:
10.1002/j.1532-2149.2014.494.x.
PMID24664788.
S2CID34286049.
^Sasaki, Y. F.; Ohta, T.; Imanishi, H.; Watanabe, M.; Matsumoto, K.; Kato, T.; Shirasu, Y. (1990). "Suppressing effects of vanillin, cinnamaldehyde, and anisaldehyde on chromosome aberrations induced by X-rays in mice". Mutation Research. 243 (4): 299–302.
doi:
10.1016/0165-7992(90)90146-b.
PMID2325694.