trans-Anethole

Description

(E)-Anethol is a phenylpropanoid that has been found in P. anisum seed oil and has antifungal and antioxidant activity. It is active against fermentatively growing S. cerevisiae under hypoxic, but not normoxic, conditions (MIC = 100 μg/ml), and against C. parapsilosis when used at a concentration of 15% w/w. (E)-Anethol has antioxidant activity in a Trolox equivalent antioxidant capacity (TEAC) assay but does not scavenge 2,2-diphenyl-1-picrylhydrazel (DPPH) radicals in a cell-free assay.

Description

Anethole, formally 1-methoxy-4-[(1E)-prop-1-en-1-yl]benzene, is an anisole derivative that is the major constituent of the oils of anise (Pimpinella anisum), star anise (Illicium verum), and fennel (Foeniculum vulgare). Also known as “anise camphor”, it is used as a flavoring and aroma agent.
Fragrant oils have been extracted from anise and fennel plants since the Renaissance, but not until 1866 did German chemist Emil Erlenmeyer (of the eponymous flask) establish the structure of the primary substance derived from these oils. Most commercial anethole is currently derived from tree extracts such as turpentine. It is generally recognized as safe (GRAS) for use in foods, cosmetics, and pharmaceuticals.
Anethole is highly hydrophobic but soluble in ethanol, a combination that produces the “ouzo effect”. When ouzo and other anise-flavored liqueurs such as absinthe and arak are poured over ice or mixed with water, the mixtures spontaneously form highly stable emulsions. The ouzo effect is a potential mechanism for designing commercial surfactant-free emulsions without the need for expensive high-speed stabilization.

Chemical properties

trans-anethole is a clear colorless to pale yellow liquid and has a characteristic anise, sweet, spicy, warm odor and corresponding sweet taste.

Anethole (1-methoxy-4-propenyl-benzene, isoestragole) is an alkoxypropenylbenzene derivative and an important favoring component of essential oils of more than 20 plant species. Essential oils from seeds of anise (Pimpinellaanisum L.), star anise (Illicium verum Hook.f), and sweet fennel (Foeniculum vulgare Mill. var. dulce) are the main sources used for the isolation of anethole. Two isomers of anethole occur in nature: E- or trans-anethole and Z-or cis-anethole. About 90 % of natural anethole is trans-isomer. Besides separation from natural essential oils, anethole is obtained using the rectification of crude sulfate turpentine and/or the organic synthesis starting from methylchavicol or anisole and propionic anhydride. Compared to natural compound, synthetic trans-anethole is impurified with higher amounts of cis-isomer.

Occurrence

Anethole is methyl ether of oestrone and has been found in fennel, aniseed, coriander, and many other volatile oils.

The Uses of trans-Anethole

trans-Anethole is used to inhibits lung and forestomach carcinogenesis, used as carbon and energy supplement in the culture media of Pseudomonas putida strain. It is also used as used as a flavoring substance.

The Uses of trans-Anethole

expectorant, gastric stimulant, insecticide

The Uses of trans-Anethole

platelet aggregation inhibitor

The Uses of trans-Anethole

flavoring agent in food, dentifrices, etc.; in perfumery for soap, etc.; in pharmaceuticals as flavor; in photography and in embedding materials in microscopy; some perfumery uses (fennei; absinthe; Hyacinth jacinthe; detergents; magnolia). Natural occurrence: star anise

Preparation

By esterification of p-cresol with methyl alcohol and with subsequent condensation with α-cetaldehyde (Perknis); the most common method of preparation is from pine oil. By fractional distillation of the essential oils of anise, star anise, and fennel; the anise essences contain an average of 85% anethole; fennel, from 60 to 70%.

Preparation

By isomerization of estragole using alcoholic potassium hydroxide as agent (Arctander, 1969).

Definition

ChEBI: Anethole is a monomethoxybenzene that is methoxybenzene substituted by a prop-1-en-1-yl group at position 4. It has a role as a plant metabolite.

Taste threshold values

Taste characteristics at 10 ppm: sweet, anise, licorice and spicy with a lingering, sweet aftertaste.

Synthesis Reference(s)

The Journal of Organic Chemistry, 50, p. 1797, 1985 DOI: 10.1021/jo00211a002
Tetrahedron, 24, p. 2183, 1968 DOI: 10.1016/0040-4020(68)88120-7

General Description

trans-Anethole is a naturally occuring flavouring agent. It has insecticidal, larvicidal, and antimicrobial properties.

Biochem/physiol Actions

Naturally occurring phenylpropene derivative that is estrogenic at lower concentrations and cytotoxic at higher concentrations to cancer cell lines. The cytotoxicity is related to the metabolism of trans-anethole to 4-hydroxy-1-propenylbenzene.

Anticancer Research

It is one of the major constituents of essential oil of fennel and anise and belongs tothe class of phenylpropenes. It has the capacity to block both inflammation andcarcinogenesis. It is an antioxidant and also a suppressor of NF-κB activation byIκBα degradation (Aggarwal and Shishodia 2004).

Metabolism

Not Available

Metabolism

Anethole is metabolized by oxidation of the propenyl group and is excreted as anisic acid (Williams, 1959). The metabolism of trans-anethole used in the preparation of anis-flavoured alcoholic beverages was studied in the rabbit and rat after iv and oral administration. It was excreted rapidly from the animal regardless of the method of administration. After iv injection it was found concentrated in the liver, lungs and brain; after oral administration, absorption was slight and most of it remained in the stomach. Ethyl alcohol has no effect on the metabolism (Le Bourhis, 1968).

Solubility in organics

Miscible with alcohol and oils, poorly soluble in Propylene glycol and Glycerin.

Dosage

The FDA "White List" permits the use of Anise oil in concentrations up to 3500 ppm. (Anise oil contains more than 90% Anethole).