Carvone

Both carvones are used in the food and flavor industry. As the compound most responsible for the flavor of caraway, dill, and spearmint, carvone has been used for millennia in food. Food applications are mainly met by carvone made from limonene. R-(−)-Carvone is also used for air freshening products and, like many essential oils, oils containing carvones are used in aromatherapy and alternative medicine.

S-(+)-Carvone is also used to prevent premature sprouting of potatoes during storage, being marketed in the Netherlands for this purpose under the name Talent.

R-(−)-Carvone has been approved by the U.S. Environmental Protection Agency for use as a mosquito repellent.{{Cite web|title=Document Display (PURL) {{!}} NSCEP {{!}} US EPA|url=https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1007AOE.TXT|access-date=2020-11-10|website=nepis.epa.gov}}

File:Carvone.svg

Carvone has two mirror image forms, or enantiomers: R-(−)-carvone, the sweetish minty smell of spearmint leaves. Its mirror image, S-(+)-carvone, has a spicy aroma with notes of rye, and gives caraway seeds their smell.{{cite journal | doi = 10.1021/jf60176a035 | title=Chemical and sensory data supporting the difference between the odors of the enantiomeric carvones |author1=Theodore J. Leitereg |author2=Dante G. Guadagni |author3=Jean Harris |author4=Thomas R. Mon |author5=Roy Teranishi | journal=J. Agric. Food Chem. | volume=19 | issue=4 | year=1971 | pages=785–787}}{{Cite journal|doi=10.1016/B978-0-12-416641-7.00035-3|title=Carvone (Mentha spicata L.) Oils - Essential Oils in Food Preservation, Flavor and Safety - Chapter 35 | year=2016|journal=Essential Oils in Food Preservation, Flavor and Safety|pages=309–316 | last1 = Morcia | first1 = Caterina | last2 = Tumino | first2 = Giorgio | last3 = Ghizzoni | first3 = Roberta | last4 = Terzi | first4 = Valeria}}

The fact that the two enantiomers are perceived as smelling different is evidence that olfactory receptors must respond more strongly to one enantiomer than to the other. Not all enantiomers have distinguishable odors. Squirrel monkeys have also been found to be able to discriminate between carvone enantiomers.{{cite journal | last1 = Laska | first1 = M. | last2 = Liesen | first2 = A. | last3 = Teubner | first3 = P. | year = 1999 | title = Enantioselectivity of odor perception in squirrel monkeys and humans| journal = American Journal of Physiology. Regulatory, Integrative and Comparative Physiology | volume = 277 | issue = 4| pages = R1098–R1103 | doi=10.1152/ajpregu.1999.277.4.r1098| pmid = 10516250}}

The two forms are also referred to, in older texts, by their optical rotations of laevo (l) referring to R-(−)-carvone, and dextro (d) referring to S-(+)-carvone. Modern naming refers to levorotatory isomers with the sign (−) and dextrorotatory isomers with the sign (+) in the systematic name.

S-(+)-Carvone is the principal constituent (60–70%) of the oil from caraway seeds (Carum carvi),Hornok, L. Cultivation and Processing of Medicinal Plants, John Wiley & Sons, Chichester, UK, 1992. which is produced on a scale of about 10 tonnes per year. It also occurs to the extent of about 40–60% in dill seed oil (from Anethum graveolens), and also in mandarin orange peel oil. R-(−)-Carvone is also the most abundant compound in the essential oil from several species of mint, particularly spearmint oil (Mentha spicata), which is composed of 50–80% R-(−)-carvone.[http://scienceofacne.com/mint-essential-oil/] {{Webarchive|url=https://web.archive.org/web/20120410220726/http://scienceofacne.com/mint-essential-oil/|date=2012-04-10}}, Chemical composition of essential oil from several species of mint (Mentha spp.) Spearmint is a major source of naturally produced R-(−)-carvone. However, the majority of R-(−)-carvone used in commercial applications is synthesized from R-(+)-limonene.{{cite book |doi=10.1002/14356007.a11_141 |chapter=Flavors and Fragrances |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2003 |last1=Fahlbusch |first1=Karl-Georg |last2=Hammerschmidt |first2=Franz-Josef |last3=Panten |first3=Johannes |last4=Pickenhagen |first4=Wilhelm |last5=Schatkowski |first5=Dietmar |last6=Bauer |first6=Kurt |last7=Garbe |first7=Dorothea |last8=Surburg |first8=Horst |isbn=978-3-527-30673-2}} The R-(−)-carvone isomer also occurs in kuromoji oil. Some oils, like gingergrass oil, contain a mixture of both enantiomers. Many other natural oils, for example peppermint oil, contain trace quantities of carvones.

Caraway was used for medicinal purposes by the ancient Romans, but carvone was probably not isolated as a pure compound until Franz Varrentrapp (1815–1877) obtained it in 1849.Handwörterbuch der reinen und angewandten Chemie [Concise dictionary of pure and applied chemistry] (Braunschweig, (Germany): Friedrich Vieweg und Sohn, 1849), vol. 4, [https://books.google.com/books?id=dIEMAQAAIAAJ&pg=PA686 pages 686-688]. [Notes: (1) Varrentrapp purified carvone by mixing oil of caraway with alcohol that had been saturated with hydrogen sulfide and ammonia; the reaction produced a crystalline precipitate, from which carvone could be recovered by adding potassium hydroxide in alcohol to the precipitate, and then adding water; (2) Varrentrapp's empirical formula for carvone is incorrect because chemists at that time used the wrong atomic masses for the elements; e.g., carbon (6 instead of 12).] It was originally called carvol by Schweizer. Goldschmidt and Zürrer identified it as a ketone related to limonene,Heinrich Goldschmidt and Robert Zürrer (1885) [http://gallica.bnf.fr/ark:/12148/bpt6k90702f/f1731.item.r=.zoom "Ueber das Carvoxim,"] Berichte der Deutschen Chemischen Gesellschaft, 18 : 1729–1733. and the structure was finally elucidated by Georg Wagner (1849–1903) in 1894.Georg Wagner (1894) [http://gallica.bnf.fr/ark:/12148/bpt6k90735d/f492.image.langEN "Zur Oxydation cyklischer Verbindungen"] (On the oxidation of cyclic compounds), Berichte der Deutschen chemischen Gesellschaft zu Berlin, vol. 27, pages 2270-2276. [Notes: (1) Georg Wagner (1849–1903) is the Germanized form of "Egor Egorovich Vagner", who was born in Russia and worked in Warsaw (See [http://www.encyclopedia.com/doc/1G2-2830904423.html brief biography here].); (2) Wagner did not prove the structure of carvone in this paper; he merely proposed it as plausible; its correctness was proved later.]

Carvone can be obtained from natural sources but insufficient is available to meet demand. Instead most carvone is produced from limonene.

The dextro-form, S-(+)-carvone is obtained practically pure by the fractional distillation of caraway oil. The levo-form obtained from the oils containing it usually requires additional treatment to produce high purity R-(−)-carvone. This can be achieved by the formation of an addition compound with hydrogen sulfide, from which carvone may be regenerated by treatment with potassium hydroxide followed by steam distillation.

Carvone may be synthetically prepared from limonene by first treating limonene nitrosyl chloride. Heating this nitroso compound gives carvoxime. Treating carvoxime with oxalic acid yields carvone.{{cite journal | doi = 10.1021/ed057p741 | volume=57 | issue=10 | title=Conversion of (+)-Limonene to (−)-Carvone: An organic laboratory sequence of local interest | year=1980 | journal=Journal of Chemical Education | page=741 | last1 = Rothenberger | first1 = Otis S. | last2 = Krasnoff | first2 = Stuart B. | last3 = Rollins | first3 = Ronald B.| bibcode=1980JChEd..57..741R }} This procedure affords R-(−)-carvone from R-(+)-limonene.

The major use of d-limonene is as a precursor to S-(+)-carvone. The large scale availability of orange rinds, a byproduct in the production of orange juice, has made limonene cheaply available, and synthetic carvone correspondingly inexpensively prepared.Karl-Georg Fahlbusch, Franz-Josef Hammerschmidt, Johannes Panten, Wilhelm Pickenhagen, Dietmar Schatkowski, Kurt Bauer, Dorothea Garbe, Horst Surburg "Flavors and Fragrances" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim {{doi|10.1002/14356007.a11_141}}

The biosynthesis of carvone is by oxidation of limonene.

There are three double bonds in carvone capable of reduction; the product of reduction depends on the reagents and conditions used. Catalytic hydrogenation of carvone (1) can give either carvomenthol (2) or carvomenthone (3). Zinc and acetic acid reduce carvone to give dihydrocarvone (4). MPV reduction using propan-2-ol and aluminium isopropoxide effects reduction of the carbonyl group only to provide carveol (5); a combination of sodium borohydride and CeCl₃ (Luche reduction) is also effective. Hydrazine and potassium hydroxide give limonene (6) via a Wolff–Kishner reduction.

Image:Carvone reduction.png

Oxidation of carvone can also lead to a variety of products. In the presence of an alkali such as Ba(OH)₂, carvone is oxidised by air or oxygen to give the diketone 7. With hydrogen peroxide the epoxide 8 is formed. Carvone may be cleaved using ozone followed by steam, giving dilactone 9, while KMnO₄ gives 10.

Image:Carvone oxidation.png

As an α,β;-unsaturated ketone, carvone undergoes conjugate additions of nucleophiles. For example, carvone reacts with lithium dimethylcuprate to place a methyl group trans to the isopropenyl group with good stereoselectivity. The resulting enolate can then be allylated using allyl bromide to give ketone 11.{{cite journal

| author = Srikrishna, A.

|author2=Jagadeeswar Reddy, T.

| year = 1998

| title = Enantiospecific synthesis of (+)-(1S, 2R, 6S)-1, 2-dimethylbicyclo [4.3. 0] nonan-8-one and (−)-7-epibakkenolide-A

| journal = Tetrahedron

| volume = 54

| issue = 38

| pages = 11517–11524

| doi = 10.1016/S0040-4020(98)00672-3

}}

Image:Carvone conj alkylation.png

Being available inexpensively in enantiomerically pure forms, carvone is an attractive starting material for the asymmetric total synthesis of natural products. For example, (S)-(+)-carvone was used to begin a 1998 synthesis of the terpenoid quassin:(a) Shing, T. K. M.; Jiang, Q; Mak, T. C. W. J. Org. Chem. 1998, 63, 2056-2057. (b) Shing, T. K. M.; Tang, Y. J. Chem. Soc. Perkin Trans. 1 1994, 1625

:Image:Quassin synthesis.png

In 1908, it was reported that exposure of carvone to "Italian sunlight" for one year gives carvone-camphor.{{cite journal |author1=Ciamician, G. |author2=Silber. P. |journal= Ber. |year= 1908 |volume= 41 |pages= 1928 |doi= 10.1002/cber.19080410272 |title= Chemische Lichtwirkungen |issue= 2|url=https://zenodo.org/record/1425988}} See enone–alkene cycloadditions.

In the body, in vivo studies indicate that both enantiomers of carvone are mainly metabolized into dihydrocarvonic acid, carvonic acid and uroterpenolone.{{cite journal | author = Engel, W. | journal = J. Agric. Food Chem. | year = 2001 | volume = 49 | issue = 8 | pages = 4069–4075 | doi = 10.1021/jf010157q | pmid = 11513712 | title = In vivo studies on the metabolism of the monoterpenes S-(+)- and R-(−)-carvone in humans using the metabolism of ingestion-correlated amounts (MICA) approach}} (–)-Carveol is also formed as a minor product via reduction by NADPH. (+)-Carvone is likewise converted to (+)-carveol.{{cite journal |author1=Jager, W. |author2=Mayer, M. |author3=Platzer, P. |author4=Reznicek, G. |author5=Dietrich, H. |author6=Buchbauer, G. | journal = Journal of Pharmacy and Pharmacology | year = 2000 | volume = 52 | pages = 191–197 | doi = 10.1211/0022357001773841 | pmid = 10714949 | title = Stereoselective metabolism of the monoterpene carvone by rat and human liver microsomes | issue = 2|s2cid=41116690 | doi-access = free }} This mainly occurs in the liver and involves cytochrome P450 oxidase and (+)-trans-carveol dehydrogenase.

{{Reflist}}

• [http://www.periodicvideos.com/videos/mv_carvone.htm Carvone] at The Periodic Table of Videos (University of Nottingham)

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Category:Flavors

Category:Enones

Category:Monoterpenes

Category:Cyclohexenes

Category:Isopropenyl compounds