Thujone

Thujone... you're probably thinking what the heck is that, how is this even in the food category and how is it toxic?
Well...
Let's first focus on what is it and where it is found:

Thujone is a ketone and a monoterpene compound that comes in two diastereomeric forms: alpha, and beta.
File:Beta-thujone.pngHere, we are looking specifically at the beta type.
Thujone - both α-thujone, and β-Thujone are toxins found naturally in many different types of essential oils including sage (Salvia officinalis), clary (Salvia sclarea), tansy (Tanacetum vulgare), wormwood (Artemisia spp.), and white cedar.
Oils from these plants are often used in the flavoring of food (due to their menthol taste), herbal medicines, and alcoholic drinks. The most well known drink made from Thujone is Absinthe (made from wormwood). Because of Thujone's well known toxic effects, both alpha and beta-thujone in food and beverages is regulated by law in many different countries.In the US, thujone as an isolated substance is banned as an ingredient to be added to food and many of the natural thujone-containing plant oils (e.g., wormwood, white cedar, oak moss (Evernia prunastri) and tansy) are used as flavorings in food under the condition that the finished food is thujone-free Absinthe (made from wormwood) contains significant levels of thujone and is available in Spain, Denmark and Portugal and so, in the US, Absinthe needs to be thujone-free to be sold. Wormwood itself is a popular flavoring for vodka in Sweden, while vermouth, chartreuse, and Benedictine all contain small levels of thujone. Since Thujone is in all of these plants that are often used for flavor, Thujone is in the food category.


So how is it toxic?
Thujone's toxins to humans have not been thoroughly researched (as it is illegal). However, we do know that thujone are noncompetitive blockers of the gamma-aminobutyric acid (GABA)-gated chloride channel and from a series of research, it has been found that high doses of thujone have been shown to cause convulsions. Thujone is also thought to be related to absinthism (the syndrome that is produced by chronically drinking absinthe) - it's characterized by addiction, hyper-excitability, and hallucinations. Not only that, in a case in 1997 that was studied by Reese, a male subject drank about 10 ml of essential oil of wormwood under the impression that itwas in fact absinthe. He was found several hours later agitated, incoherent,and disoriented. Over time, his health did improve with treatment but he subsequently developed acute renal failure.
Below, is an image of what happens when a mouse takes thujone.
(click on it to see the change)



How much do you have to take before toxic effects hit?
For humans, it is unknown. But, studies in rats, mouse, and other animals have shown the doses that cause convulsion below.

Animal

Product Administered/Route

Convulsive Dose (mg/kg)

Reference

 

Rat

α-thujone + β-Thujone / intraperitoneal (i.p.)

100

Sampson & Fernandez, 1973

 

Rabbit

α-thujone / intravenous (i.v.)

4

Keith & Stavasky 1935

 

Mouse

α-thujone + β-Thujone / intra-peritoneal (i.p.)

260

Wenzel & Ross, 1957


Cat

α-thujone / intravenous (i.p.)
α-thujone / intravenous (i.p.)

7

20

Keith & Stavasky 1935

 




Here, we can see the range for this varies greatly - anything from 4-260 mg/kg can cause a convulsive dose... so what is "safe" level?

Toxic Effects Continued...
Well, let's try the LD50 - it may give us more information. So how much thujone do you give so that 50% of the population dies (whatever population it is - most likely not human, again - it's not legal)?
Route
Species
LD50 (mg/kg)
Reference
Oral
Rat
500
NLM, 1997a
Intravenous
Rabbit
0.031
NLM, 1997a
Subcutaneous
Mouse

 

Mouse

 

Rabbit
2.157

 

87.5

 

0.362
NLM, 1997a

Rice & Wilson, 1976

NLM, 1997a

Dermal
Rabbit
5000
FEMA, 1997

As we can see, even these doses for different types of mammals vary greatly. Anything from a really small amount of 0.031 mg/kg to 5000mg/kg. From this and previous results, we can see that toxic effects for thujone varies greatly in species - so a lot of interspecies differences. This means that, for humans, toxic effects This is obviously due to interspecies differences - but, from this, we can really consider... should we take our chances?


Summary
We know that thujone is toxic, but it is unknown how much thujone is really needed for toxic effects to occur in humans. But, considering that thujone is in many of the essential flavoring oils we use in food, and alcohol it is important to be wary until more recent research are made. Unfortunately, since many of the research done on toxic effects of thujone are done quite a while ago, their results may or may not be extremely accurate. Not only that, it's important to look further into how much thujone is actually in our everyday lives. Yes, many products claim to be "thujone-free" in the United States - and that's how they can be sold, but there are no guarantees and until further research proves that there's no thujone in those products or proof that small amounts of thujone in products in not harmful, I think we should be wary. Why? Well, thujone-free doesn't mean it's completely free of thujone - thujone free just means there are little to no thujone (so there can be traces of thujone and as we can see, even a small amount can be toxic). Not only that, traces of thujone here, and traces of thujone there can soon add up. So - in the end, it may be better to take some caution and read labels, while paying careful attention to alcohol and things that has natural flavoring from wormwood, white cedar, oak moss, sage, thyme, etc.
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