Thujone

Thujone (C₁₀H₁₆O) is a chemical compound. It is a colourless liquid with a distinctive menthol odour, it is a ketone, a monopterpene, and is found in two stereoisomeric forms - (+)-3-thujone or α-thujone and (-)-3-thujone or β-thujone. It boils at 201°C, is insoluble in water although it is readily soluble in ethanol or diethyl ether.

It is found in certain plants such as juniper, mugwort, sage, yellow cedar and wormwood, usually as a mix of isomers in a 1:2 ratio. Its name is sometimes given structurally as bicyclo(3.1.0)hexan-3-one, 4-methyl-1-(1-methylethyl)-,(1S-(1-, 4-, 5-α))-(9CI), other names used 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 is best known as a component of the drink absinthe, as it is a natural oil of wormwood (Artemisia absinthium). Although the compound is credited with hallucinogenic properties this is not certain; it is structurally close to THC and is certainly toxic but each isomer has distinct differences.