Anethole

Anethole (also known as anise camphor)<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is an organic compound that is widely used as a flavoring substance. It is a derivative of the aromatic compound allylbenzene and occurs widely in the essential oils of plants. It is in the class of phenylpropanoid organic compounds. It contributes a large component of the odor and flavor of anise and fennel (both in the botanical family Apiaceae), anise myrtle (Myrtaceae), liquorice (Fabaceae), magnolia blossoms, and star anise (Schisandraceae). Closely related to anethole is its isomer estragole, which is abundant in tarragon (Asteraceae) and basil (Lamiaceae), and has a flavor reminiscent of anise. It is a colorless, fragrant, mildly volatile liquid.Template:Clarify<ref name=Ullmann>Template:Ullmann</ref> Anethole is only slightly soluble in water but exhibits high solubility in ethanol. This trait causes certain anise-flavored liqueurs to become opaque when diluted with water; this is called the ouzo effect.

Structure and production

Anethole is an aromatic, unsaturated ether related to lignols. It exists as both cis–trans isomers (see also E–Z notation), involving the double bond outside the ring. The more abundant isomer, and the one preferred for use, is the trans or E isomer.<ref name="chemistry-europe.onlinelibrary.wiley.com">Template:Cite journal</ref>

Like related compounds, anethole is poorly soluble in water. Historically, this property was used to detect adulteration in samples.<ref>Template:Cite journal</ref>

Most anethole is obtained from turpentine-like extracts from trees.<ref name=Ullmann /><ref>Template:Cite patent</ref> Of only minor commercial significance, anethole can also be isolated from essential oils.<ref>Template:Cite book</ref><ref name="Ashurst">Template:Cite bookTemplate:Dead link</ref><ref>Template:Cite journal</ref>

Essential oil	World production	Trans-anethole
Anise	8 tonnes (1999)	95%
Star anise	400 tonnes (1999), mostly from China	87%
Fennel	25 tonnes (1999), mostly from Spain	70%

Currently Banwari Chemicals Pvt Ltd situated in Bhiwadi, Rajasthan, India is the leading manufacturer of anethole. It is prepared commercially from 4-methoxypropiophenone,<ref name="chemistry-europe.onlinelibrary.wiley.com"/><ref>Template:Cite journal</ref> which is prepared from anisole.<ref name=Ullmann />

Uses

Flavoring

Anethole is distinctly sweet, measuring 13 times sweeter than sugar. It is perceived as being pleasant to the taste by many even at higher concentrations. It is used in alcoholic drinks ouzo, rakı, anisette and absinthe, among others. It is also used in seasoning and confectionery applications, such as German Lebkuchen, oral hygiene products, and in small quantities in natural berry flavors.<ref name="Ashurst" />

Precursor to other compounds

Because they metabolize anethole into several aromatic chemical compounds, some bacteria are candidates for use in commercial bioconversion of anethole to more valuable materials.<ref name="pmid11805095" /> Bacterial strains capable of using trans-anethole as the sole carbon source include JYR-1 (Pseudomonas putida)<ref name="pmid16028980">Template:Cite journal</ref> and TA13 (Arthrobacter aurescens).<ref name="pmid11805095">Template:Cite journal</ref>

Research

Antimicrobial and antifungal activity

Anethole has potent antimicrobial properties, against bacteria, yeasts, and fungi.<ref name="pmid11807977">Template:Cite journal</ref> Reported antibacterial properties include both bacteriostatic and bactericidal action against Salmonella enterica<ref name="pmid11743758">Template:Cite journal</ref> but not when used against Salmonella via a fumigation method.<ref name="pmid11307877">Template:Cite journal</ref> Antifungal activity includes increasing the effectiveness of some other phytochemicals (such as polygodial) against Saccharomyces cerevisiae and Candida albicans;<ref name="pmid17078111">Template:Cite journal</ref>

In vitro, anethole has antihelmintic action on eggs and larvae of the sheep gastrointestinal nematode Haemonchus contortus.<ref name="pmid17629623">Template:Cite journal</ref> Anethole also has nematicidal activity against the plant nematode Meloidogyne javanica in vitro and in pots of cucumber seedlings.<ref name="pmid18944489">Template:Cite journal</ref>

Insecticidal activity

Anethole also is a promising insecticide. Several essential oils consisting mostly of anethole have insecticidal action against larvae of the mosquito Ochlerotatus caspius<ref name="pmid17368893">Template:Cite journal</ref> and Aedes aegypti.<ref name="pmid15237942">Template:Cite journal</ref><ref name="pmid16646345">Template:Cite journal</ref> In a similar manner, anethole itself is effective against the fungus gnat Lycoriella ingenua (Sciaridae)<ref name="pmid16786497">Template:Cite journal</ref> and the mold mite Tyrophagus putrescentiae.<ref name="pmid15954709">Template:Cite journal</ref> Against the mite, anethole is a slightly more effective pesticide than DEET, but anisaldehyde, a related natural compound that occurs with anethole in many essential oils, is 14 times more effective.<ref name="pmid15954709" /> The insecticidal action of anethole is greater as a fumigant than as a contact agent. trans-Anethole is highly effective as a fumigant against the cockroach Blattella germanica<ref name="pmid11852640">Template:Cite journal</ref> and against adults of the weevils Sitophilus oryzae, Callosobruchus chinensis and beetle Lasioderma serricorne.<ref name="pmid11455661">Template:Cite journal</ref>

As well as an insect pesticide, anethole is an effective insect repellent against mosquitos.<ref name="pmid12963152">Template:Cite journal</ref>

Ouzo effect

File:Preparing absinthe.jpg

Diluting absinthe with water produces a spontaneous microemulsion (ouzo effect)

Anethole is responsible for the "ouzo effect" (also "louche effect"), the spontaneous formation of a microemulsion<ref name="Sitnikova+2005">Template:Cite journal</ref><ref>Template:Cite journal</ref> that gives many alcoholic beverages containing anethole and water their cloudy appearance.<ref name="Sanchez-Dominguez Rodriguez-Abreu 2016 p. 369">Template:Cite book</ref> Such a spontaneous microemulsion has many potential commercial applications in the food and pharmaceutical industries.<ref name="pmid17229398">Template:Cite journal</ref>

Precursor to illicit drugs

Anethole is an inexpensive chemical precursor for paramethoxyamphetamine (PMA),<ref name="pmid12742705">Template:Cite journal</ref> and is used in its clandestine manufacture.<ref name="pmid15240033">Template:Cite journal</ref> Anethole is present in the essential oil from guarana, which has psychoactive effects typically attributed to its caffeine content. The absence of PMA or any other known psychoactive derivative of anethole in human urine after ingestion of guarana leads to the conclusion that any psychoactive effect of guarana is not due to aminated anethole metabolites.<ref name="pmid8765992">Template:Cite journal</ref>

Anethole is also present in absinthe, a liquor with a reputation for psychoactive effects; these effects, however, are attributed to ethanol.<ref name="pmid18429531">Template:Cite journal</ref> (See also thujone, anethole dithione (ADT), and anethole trithione (ATT).)

Estrogen and prolactin

Anethole has estrogenic activity.<ref name="Jordan1986">Template:Cite book</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> It has been found to significantly increase uterine weight in immature female rats.<ref name="TisserandYoung2013">Template:Cite book</ref>

Fennel, which contains anethole, has been found to have a galactagogue effect in animals. Anethole bears a structural resemblance to catecholamines like dopamine and may displace dopamine from its receptors and thereby disinhibit prolactin secretion, which in turn may be responsible for the galactagogue effects.<ref name="BoneMills2013">Template:Cite book</ref>

Safety

In the USA, anethole is generally recognized as safe (GRAS). After a hiatus due to safety concerns, anethole was reaffirmed by Flavor and Extract Manufacturers Association (FEMA) as GRAS.<ref name="pmid10496381">Template:Cite journal</ref> The concerns related to liver toxicity and possible carcinogenic activity reported in rats.<ref name="pmid2467866">Template:Cite journal</ref> Anethole is associated with a slight increase in liver cancer in rats,<ref name="pmid2467866" /> although the evidence is scant and generally regarded as evidence that anethole is not a carcinogen.<ref name="pmid2467866" /><ref name="pmid12151622">Template:Cite journal</ref> An evaluation of anethole by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) found its notable pharmacologic properties to be reduction in motor activity, lowering of body temperature, and hypnotic, analgesic, and anticonvulsant effects.<ref name="JECFA466">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> A subsequent evaluation by JECFA found some reason for concern regarding carcinogenicity, but there is currently insufficient data to support this.<ref name="JECFA717">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> At this time, the JECFA summary of these evaluations is that anethole has "no safety concern at current levels of intake when used as a flavoring agent".<ref name="JECeval">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

In large quantities, anethole is slightly toxic and may act as an irritant.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

History

That an oil could be extracted from anise and fennel had been known since the Renaissance by the German alchemist Hieronymus Brunschwig (Template:Circa), the German botanist Adam Lonicer (1528–1586), and the German physician Valerius Cordus (1515–1544), among others.<ref name="semmler">See:

• Template:Cite book
• Template:Cite book
• Template:Cite book</ref> Anethole was first investigated chemically by the Swiss chemist Nicolas-Théodore de Saussure in 1820.<ref>Template:Cite journal See especially pp. 280–284.</ref> In 1832, the French chemist Jean Baptiste Dumas determined that the crystallizable components of anise oil and fennel oil were identical, and he determined anethole's empirical formula.<ref>See:
• Template:Cite journal On p. 234, Dumas provides an empirical formula C₁₀H₆O_{Template:Sfrac} for anethol. If the subscripts are doubled and if the subscript for carbon is then halved (because Dumas, like many of his contemporaries, used the wrong atomic mass for carbon, 6 instead of 12), then Dumas' empirical formula is correct.
• Dumas' finding that the crystallizable components of anise oil and fennel oil were identical was confirmed in 1833 by the team of Rodolphe Blanchet (1807–1864) and Ernst Sell (1808–1854). See: Template:Cite journal See especially pp. 287–288.
• Dumas' empirical formula for anethole was confirmed in 1841 by the French chemist Auguste Cahours. See: Template:Cite journal See pp. 278–279. Note that the subscripts of Cahours' empirical formula (C₄₀H₂₄O₂) must be divided by 2 and then the subscript for carbon must be divided again by 2 (because, like many chemists of his time, Cahours used the wrong atomic mass for carbon, 6 instead of 12). If these changes are made, the resulting empirical formula is correct.</ref> In 1845, the French chemist Charles Gerhardt coined the term anethol – from the Latin anethum (anise) + oleum (oil) – for the fundamental compound from which a family of related compounds was derived.<ref>Template:Cite journal</ref> Although the German chemist Emil Erlenmeyer proposed the correct molecular structure for anethole in 1866,<ref>Template:Cite journal</ref> it was not until 1872, that the structure was accepted as correct.<ref name="semmler"/>

See also

• Category:Anise liqueurs and spirits
• List of liqueurs § Anise-flavored liqueurs
• Anol
• Chavicol
• Dianethole
• Fenchone
• Pseudoisoeugenol
• Safrole

External links

• Template:Commons category-inline