Thujone

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Thujone (C₁₀H₁₆O) is a chemical compound. It is a colourless liquid with a distinctive menthol odour. It is a ketone and a monoterpene, and is found in two stereoisomeric forms: (+)-3-thujone or α-thujone and (-)-3-thujone or β-thujone. Its formal name is sometimes given as bicyclo(3.1.0)hexan-3-one, 4-methyl-1-(1-methylethyl)-,(1S-(1-, 4-, 5-α))-(9CI); other names include isothujone and thujanone. It is used as a flavouring agent in certain foods and is a compound in a number of other food additives. It boils at 201°C and is insoluble in water although it is readily soluble in ethanol or diethyl ether.

Sources

Thujone is found in a number of plants, such as arborvitae (genus Thuja, whence the derivation of the name), Nootka Cypress, some junipers, mugwort, sage, tansy (25-77% in essential oil) and wormwood, most notably the Artemisia absinthium species, usually as a mix of isomers in a 1:2 ratio.

Pharmacology

The chemical structure of thujone is loosely related to that of THC and it was formerly believed to have a similar structure-activity mechanism, but this has now been disproved. It is now believed that it antagonizes inhibition in the gamma-aminobutyric acid (GABA) receptor system.

In mice the LD50 is around 45 mg/kg. 0% mortality rate at 30 mg/kg and 100% at 60 mg/kg. Those exposed to the higher dose had convulsions that lead to death in 1 minute. From 30 to 45 mg/kg the mice would experience muscle spasms in the legs which progressed to general convulsions until death or recovery. Pretreatment of diazepam, phenobarbital or 1 g/kg of ethanol protected against a lethal 100 mg/kg dose. [1]

There are few studies on humans and the LD50 isn't known. One study in the "journal of alcohol studies" administered 0.28 mg/kg thujone in alcohol, 0.028 mg/kg in alcohol and just alcohol to subjects. The high dose had a negative effect on attention performance. The lower dose showed no noticeable effect. [2]

It is best known as a component of the drink absinthe, as it is a component of natural oil of wormwood (Artemisia absinthium). Although it was believed to be the cause of absinthism, an alleged syndrome which caused epileptic fits and hallucinations in chronic absinthe drinkers this has since been questioned. New studies of vintage absinthe, modern absinthe made with vintage recipes and modern absinthe show very little thujone. Most absinthe studied including the vintage were below 10 mg/kg and all were below EU regulations for bitters. [3] [4]

Regulations

European Union

maximum thujone levels in the EU. [5]

• 0.5 mg/kg in food not prepared with sage and non alcoholic beverages.
• 5 mg/kg in alcoholic beverages with 25% or less ABV
• 10 mg/kg in alcoholic beverages with more than 25% ABV
• 25 mg/kg in food prepared with sage.
• 35 mg/kg in alcohol labeled as bitters.

United States

Foods or beverages that contain Artemisia species, white cedar, oak moss, tansy or Yarrow must be thujone free.[6] Other herbs that contain thujone have no restrictions. For example, sage and sage oil (which can be 50%+ thujone) are on the FDA's list of Substances generally recognized as safe.