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Le Peril Vert depicts absinthe ravaging the French population. The artist, T. Bianco, was a well-known satirical illustrator.
The Chemistry of Absinthe
Though a pioneer in French psychiatry, Valentin Magnan did not transcend the biases of his time. His diagnosis of “absinthism” lent the imprimatur of medical science to what might have otherwise remained a folk belief.
Bans helped solidify absinthe’s deadly reputation in popular culture, and subsequent scientific study was often overshadowed by Magnan’s work. With the relaxation of legal restrictions, scientists again began to examine the drink, homing in on its presumed active ingredient, thujone (C10H16O). Thujone, the essence of wormwood, was long thought to be hallucinogenic—based in part on literary descriptions from the likes of Baudelaire and Rimbaud. But little science existed to support this claim.
In 1975, noting similarities in the psychological effects attributed to absinthe with those of marijuana, researchers suggested comparing thujone with tetrahydrocannabinol (THC), the active ingredient in cannabis. Thujone and THC have similar molecular geometry: both have similar functional groups available for metabolism in humans; both are terpenoids; and though this large group contains Salvinornin A, the psychotropic molecule in Salvia divinorum, it also includes fewer controversial molecules, such as camphor and menthol.
Later research proved that thujone exhibits some affinity for cannabinoid receptors but does not stimulate the same responses as THC. Any intoxicating effects are not the same as those of marijuana’s active ingredient.
Thujone does, however, inhibit GABA-receptor activation; in extremely high doses this property can cause spasms and convulsions. At least one would-be absintheur required hospitalization after overdosing on wormwood oil. Researchers hypothesized that some pre-ban absinthes may have contained similarly high quantities of thujone, but chemical analyses revealed levels much lower than previous estimates.
Many now believe it unlikely that thujone—at least in the small amounts found in absinthe—can have a toxic effect. What then caused the “absinthism” observed by Magnan and his colleagues? Some suggest that without strong regulation and quality control, such adulterants as copper sulfate, antimony, or chloride could have poisoned absinthe drinkers. And inferior alcohol, used by distillers eager to turn a quick profit, could also have led to impaired vision, for example.
But the most likely culprit is perhaps also the most obvious: ethanol. The most prominent ingredient in absinthe after all is alcohol; maintaining wormwood in solution requires greater than 50% alcohol by volume. Stripped of its singular glamour and tabloid enchantments, “absinthism” looks like a much sadder and more common affliction: chronic alcoholism.
The Chemistry of Absinthe
©2010 Chemical Heritage Foundation