Anethole

Anethole
File:Anethole-structure-skeletal.png
IUPAC name 1-methoxy-4-(1-propenyl)benzene
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number	104-46-1 Y
PubChem	637563
ChemSpider	553166
SMILES
InChI
InChI key	RUVINXPYWBROJD-ONEGZZNKBR
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula	C10H12O
Molar mass	148.2 g mol−1
Density	0.998 g/cm3
Melting point	20-21 °C
Boiling point	234 °C; 81 °C at 2 mmHg
style="background: #F8EABA; text-align: center;" colspan="2" | Hazards
MSDS	External MSDS
style="background: #F8EABA; text-align: center;" colspan="2" | Related compounds
Related compounds	Anisole; Estragole
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Anethole (also para-methoxyphenylpropene, p-propenylanisole, and isoestragole) is an aromatic compound that occurs widely in nature, in essential oils. It contributes a large component of the distinctive flavors of anise and fennel (both in the botanical family Apiaceae), anise myrtle (Myrtaceae), liquorice (Fabaceae), and star anise (Illiciaceae). Closely related to anethole is its double-bond isomer estragole, abundant in tarragon (Asteraceae) and basil (Lamiaceae), that has a flavor reminiscent of anise. Anethole has numerous commercial uses in multiple industries, and high potential for additional uses.

Structure and properties

In chemical terms, anethole is an aromatic, unsaturated ether. It has two 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: trans-anethole, t-anethole, (E)-anethole, trans-para-methoxyphenylpropene. Its full chemical name is trans-1-methoxy-4-(prop-1-enyl)benzene.

Anethole is less soluble in water than in ethanol, which causes certain anise-flavored liquours to become opaque when diluted with water (see Ouzo effect). It is a clear, colorless liquid with boiling point 234 °C and congealing point (freezing point) 20 °C; below its congealing point, anethole forms white crystals. The crystals will precipitate from an aqueous solution, which causes a "snow globe" effect when certain anise-flavored liquours are chilled. This effect is the basis of a patent for industrial purification of anethole from sources such as pine oil. Anethole can be crystallized directly from a source essential oil by lowering the temperature of the oil; adding a crystal of anethole helps to start the process. Historically, this was used to detect adulteration.

Production

Commercial sources of anethole include some essential oils:

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

Uses

Anethole is a flavoring substance of commercial value. In addition, it is distinctly sweet, measuring 13 times sweeter than sugar. It is perceived as being pleasant to the taste even at higher concentrations. It is unrelated to glycyrrhizic acid, which often co-occurs with it, and also is very sweet. Anethole is used in alcoholic drinks, seasoning and confectionery applications, oral hygiene products, and in small quantities in natural berry flavors.

Anethole is an inexpensive chemical precursor for paramethoxyamphetamine (PMA), and used in its clandestine manufacture. Anethole is present in the essential oil from guarana, which is alleged to have has a psychoactive effect; however, the absence of PMA or any other known psychoactive derivative of anethole leads to the conclusion that any purported psychoactive effect of guarana is not due to anethole. Anethole is also present in absinthe, a liquor with a reputation for psychoactive effects; these effects however are attributed to ethanol (see also Thujone).

Pharmaceutical drugs derived from or related to anethole include anisyldithiolthione, anethole dithione (ADT), and anethole trithione (ATT).

Research

File:Preparing absinthe.jpg

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

Anethole is responsible for the "ouzo 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. A derivative of anethole, anethole trithione, is being investigated for use in self-microemulsifying drug delivery systems (SMEDDS).

Bacterial strains capable of using trans-anethole as the sole carbon source include JYR-1 (Pseudomonas putida) and TA13 (Arthrobacter aurescens). Because they metabolize anethole into several aromatic chemical compounds, these bacteria are candidates for use in commercial bioconversion of these valuable compounds from anethole and other phenylpropanoids. Compared to other industrial processes, such bioconversion may be less costly and more friendly to the environment.

Anethole has potent antimicrobial properties, against bacteria, yeast, 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 phytochemicals (eg polygodial) against Saccharomyces cerevisiae and Candida albicans; this synergistic effect has potential medical uses.

In vitro, anethole has antihelmintic action on eggs and larvae of the sheep gastrointestinal nematode Haemonchus contortus. Anethole also has nematicidal activity against the plant nematode Meloidogyne javanica in vitro and in pots of cucumber seedlings.

Anethole also is a promising insecticide. Several essential oils consisting mostly of anethole have insecticidal action against larvae of the mosquitos Ochlerotatus caspius and Aedes aegypti. In 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 fumigant than as a contact agent. (E)-anethole is highly effective as a fumigant against the cockroach Blattella germanica and against adults of the weevils Sitophilus oryzae, Callosobruchus chinensis and beetle Lasioderma serricorne.

As well as an insect pesticide, anethole is an effective insect repellent against mosquitos.

Safety

Formerly generally recognized as safe (GRAS), after a hiatus anethole was reaffirmed by Flavor and Extract Manufacturers Association (FEMA) as GRAS. The hiatus was due to concerns about liver toxicity and possible carcinogenic activity, reported in rats. 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 pharmacologic 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 re carcinogenicity but insufficient data. 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.

See also

• Category:Anise liqueurs and spirits
• List of liqueurs#Anise-flavored liqueurs
• Chavicol
• Safrole
• Fenchone

External links

• Molecular Models from OUC: anetholecs:Anetol

vi:Anethol