Anethole (also known as anise camphor)
Structure and production
Anethole is an aromatic, unsaturated
ether related to
Monolignol. 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.
Like related compounds, anethole is poorly soluble in water. Historically, this property was used to detect adulteration in samples.
Most anethole is obtained from turpentine-like extracts from trees.
|
|
| 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,
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
Flavoring.
Precursor to other compounds
Because they
Metabolism anethole into several aromatic chemical compounds, some bacteria are candidates for use in commercial
bioconversion of anethole to more valuable materials.
Bacterial strains capable of using trans-anethole as the sole carbon source include JYR-1 (
Pseudomonas putida)
and TA13 (
Arthrobacter aurescens).
Research
Antimicrobial and antifungal activity
Anethole has potent
antimicrobial properties, against
bacteria,
, and
fungi.
Reported antibacterial properties include both
bacteriostatic and
bactericidal action against
Salmonella enterica but not when used against
Salmonella via a
fumigation method.
Antifungal activity includes increasing the effectiveness of some other
(such as
polygodial) against
Saccharomyces cerevisiae and
Candida albicans;
In vitro, anethole has antihelmintic action on eggs and larvae of the domestic sheep gastrointestinal nematode Haemonchus contortus.
Insecticidal activity
Anethole also is a promising insecticide. Several essential oils consisting mostly of anethole have
insecticide action against
of the
mosquito Ochlerotatus caspius and
Aedes aegypti.
In a similar manner, anethole itself is effective against the
fungus gnat Lycoriella ingenua (
Sciaridae)
and the
mold mite Tyrophagus putrescentiae.
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.
The insecticidal action of anethole is greater as a
fumigation than as a contact agent.
trans-Anethole is highly effective as a fumigant against the
cockroach Blattella germanica and against adults of the
Sitophilus oryzae,
Callosobruchus chinensis and
beetle Lasioderma serricorne.
As well as an insect pesticide, anethole is an effective insect repellent against mosquitos.
Ouzo effect
Anethole is responsible for the "
ouzo effect" (also "louche effect"), the spontaneous formation of a
microemulsion that gives many alcoholic beverages containing anethole and water their cloudy appearance.
Such a spontaneous microemulsion has many potential commercial applications in the food and pharmaceutical industries.
Precursor to illicit drugs
Anethole is an inexpensive chemical precursor for paramethoxyamphetamine (PMA),
and is used in its clandestine manufacture.
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.
Anethole is also present in absinthe, a liquor with a reputation for psychoactive effects; these effects, however, are attributed to ethanol.
Estrogen and prolactin
Anethole has
activity.
It has been found to significantly increase
uterine weight in immature female rats.
Fennel, which contains anethole, has been found to have a galactagogue effect in animals. Anethole bears a structural resemblance to like dopamine and may displace dopamine from its receptors and thereby disinhibit prolactin secretion, which in turn may be responsible for the galactagogue effects.
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.
The concerns related to liver toxicity and possible carcinogenic activity reported in
.
Anethole is associated with a slight increase in
liver cancer in rats,
although the evidence is scant and generally regarded as evidence that anethole is
not a
carcinogen.
An evaluation of anethole by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) found its notable
pharmacology properties to be reduction in motor activity, lowering of body temperature, and
hypnotic,
analgesic, and
anticonvulsant effects.
A subsequent evaluation by JECFA found some reason for concern regarding
carcinogenicity, but there is currently insufficient data to support this.
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".
In large quantities, anethole is slightly toxic and may act as an irritant.
History
That an oil could be extracted from anise and fennel had been known since the
Renaissance by the German alchemist Hieronymus Brunschwig (), the German botanist
Adam Lonicer (1528–1586), and the German physician
Valerius Cordus (1515–1544), among others.
[See:
] Anethole was first investigated chemically by the Swiss chemist Nicolas-Théodore de Saussure in 1820.
[ See especially pp. 280–284.] 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.
[See:
On p. 234, Dumas provides an empirical formula C10H6O 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: See especially pp. 287–288.
Dumas' empirical formula for anethole was confirmed in 1841 by the French chemist Auguste Cahours. See: 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.] 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.
Although the German chemist
Emil Erlenmeyer proposed the correct molecular structure for anethole in 1866,
it was not until 1872, that the structure was accepted as correct.
See also
External links
