Thujone is a naturally occurring bicyclic monoterpene ketone present in essential oils of plants such as wormwood and sage. It is widely known for its association with absinthe and potential neurotoxic effects. 

Chemical Structure and Isomers

Thujone (C₁₀H₁₆O) exists as two enantiomers: α-thujone and β-thujone. These isomers differ in the orientation of the methyl group on the cyclopentanone ring fused to a four-membered ring. α-Thujone predominates in wormwood oil and exhibits stronger biological activity due to its stereochemistry.

Both enantiomers are volatile, lipophilic compounds with camphoraceous odors, which influence their detection by gas chromatography-mass spectrometry (GC-MS) in herbal products.

Natural Sources and Extraction

Thujone is found in Artemisia absinthium (wormwood), Salvia officinalis (sage), and Tanacetum vulgare (tansy), with essential oil concentrations reaching up to 50%. Due to its neurotoxicity, regulatory limits exist for thujone in foods, beverages, and herbal medicines.

Extraction typically involves steam distillation, followed by fractional distillation to isolate thujone fractions. Beverage and herbal product levels are monitored under EMA guidelines, ranging from 0.2 to 5 mg/kg.