Potion Chemistry: The science behind Macbeth’s witches

Double, double, toil and trouble: discover the deadly ingredients added to the bubbling cauldron of Macbeth’s witches

Tongue of dog

More of a play on words than the literal ingredient, houndstongue (Cynoglossum officinale) is poisonous to livestock rather than humans. Within the leaves of this plant are pyrrolizidine alkaloids, toxins that lead to liver damage and failure. These toxins are transported to the liver through intestinal absorption and are metabolised in liver cells called hepatocytes. There they stop the process of mitosis (cell division) and cause the formation of thick, scarring connective tissue known as fibrosis, ultimately killing the liver and causing death

Eye of newt

This is one of the most commonly known ingredients in a witch’s pantry. Its name suggests the suffering of a small amphibian for a witch’s gain. However, the eye of newt is not what it seems – it may even be in your cupboard. They are, in fact, mustard seeds. While these ‘eyes’ do not hold any magical properties, they certainly pack a powerful punch in flavour. Mustard seeds can also be used to create a powerful irritant. They contain the compound sinigrin which when crushed releases an enzyme called myrosinase, forming an oil. When mixed with cold water this combination can cause blistering when applied to the skin.

Slips of yew

Yew trees (Taxus baccata) are found spread across the Northern Hemisphere, reaching heights of between ten and 15 metres. Each branch is lined with sharp blades of pine leaves that have the potential to take down a horse in 15 minutes. This tree’s deadly weapon of choice is a group of cardiotoxins called taxine alkaloids. Once ingested, taxines affect the electrical activity within the heart. These toxins can block calcium channels and reduce blood flow, resulting in death by way of ventricular fibrillation, where the heart stops pumping blood and only quivers until cardiac arrest occurs. The lethal dose for a human is 50 grams, and death will follow between two to five hours after.

Root of hemlock

The root of the North American water hemlock (Cicuta) can cause a fatal reaction to any that ingest it. Seizures, respiratory failure and tremors are just some of the precursor symptoms of this deadly plant. Its potent killing powers come from its levels of cicutoxins. Yellow in colour, these toxins are quickly absorbed by mucous membranes in the body. They can block sodium and potassium channels, which directly affects the human nervous system. This then leads to the complete failure of the respiratory system within 15 minutes of ingesting the toxin.


This article was originally published in How It Works issue 117


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