Strychnine

Some seeds are very strong.

They come from a special tree. This tree makes a bitter substance.

People use it to stop pests. It can make small animals very sick. It makes their muscles jump and twitch. It can even make them stop breathing. Some animals can eat the fruit safely. But most animals must stay away. We must be very careful with it. Have you ever seen a bitter seed?

Strychnine is a very bitter substance.

It comes from the seeds of a special tree. This tree is called Strychnos nux-vomica. People use strychnine as a pesticide. This is a way to kill pests like rats or birds.

Strychnine works by attacking the body's signals. Our bodies use chemicals to tell muscles to move. One chemical is called glycine. Glycine helps keep our muscles calm. It acts like a brake on a car. Strychnine stops glycine from doing its job. It blocks the glycine receptors, which are the parts that receive the signal.

Without the glycine signal, the muscles do not stay calm. They begin to twitch and jump. These are called muscle convulsions. The body can become very stiff. This can make it hard to breathe. This is called asphyxia.

Some animals can eat the fruit of this tree safely. For example, some fruit bats are immune. A tiny bug called the drugstore beetle can also eat it. This is because it has special yeast in its gut.

Most other animals must stay away from it.

Strychnine is a very bitter, colorless substance that looks like crystals.

It is a highly toxic chemical known as an alkaloid. Because it is so strong, people have used it as a pesticide. This helps kill small animals like rodents or birds. It is mostly found in the seeds of the Strychnos nux-vomica tree. These seeds are very hard to digest if they are swallowed whole. To work as a poison, the seeds must be crushed or chewed first.

This chemical works by interfering with how the body sends signals. Our bodies use special parts called receptors to receive messages. One important messenger is a chemical called glycine. Glycine acts like a brake to keep our muscles calm. Strychnine is an antagonist, which means it blocks that brake. It binds to the glycine receptors in the spinal cord and brain. This prevents the calming signal from getting through to the nerves. Without that brake, the nerves send too many signals to the muscles. This causes the muscles to twitch and contract very strongly.

Scientists have studied this complex molecule for a long time. It has many rings and a very tricky shape. A chemist named Sir Robert Robinson once called it very complex. He was talking about how difficult it is to understand its structure. In 1954, a researcher named Robert Burns Woodward achieved a big goal. His group completed the first total synthesis of strychnine. This means they built the molecule from scratch in a lab. He even wrote a very long report about his work in 1963.

Poisoning from strychnine is very dangerous for humans and animals. For an adult, a small amount between 30 and 120 mg can be fatal. Symptoms often appear within 15 to 60 minutes of swallowing it. The first signs include restlessness, nervousness, and neck stiffness. As it gets worse, the body experiences severe muscle convulsions. The back and neck may arch deeply in a position called opisthotonus. Eventually, the muscles used for breathing stop working. This leads to death by asphyxia, which is a lack of air.

Not every living thing reacts to strychnine the same way. Some animals have found ways to live with it. For example, some fruit bats are immune to these toxins. A tiny insect called the drugstore beetle can eat it too. This beetle has a special yeast in its gut to help it digest the poison. In the United States, most people stopped using strychnine baits in 1990. The European Union banned these types of baits in 2006. This change helped protect animals that were not the intended targets. Today, most people know strychnine from stories in books and films.

Strychnine is a highly toxic, colorless, and bitter crystalline alkaloid. It is primarily used as a pesticide to control small vertebrates, such as rodents and birds. Because it is so potent, it has a significant impact on the central nervous system. While it is no longer used in medicine, it was used historically to stimulate the heart and bowels. It was also used as a performance-enhancing drug to strengthen muscle contractions.

The most common natural source of strychnine is the seeds of the *Strychnos nux-vomica* tree. These seeds have a very hard pericarp, which is an outer layer that is difficult to digest. Because of this, the seeds often only work as a poison if they are crushed or chewed before being swallowed. If a person or animal swallows the seeds whole, the poisoning symptoms might not appear. The complex way the plant builds this molecule is called biosynthesis. In 2022, scientists solved the exact steps of how the plant creates strychnine.

Strychnine acts as a neurotoxin by working as an antagonist to glycine and acetylcholine receptors. In a healthy body, a neurotransmitter called glycine acts as an inhibitory signal. It binds to glycine receptors, which are ligand-gated chloride channels in the brain and spinal cord. When glycine binds, it allows negatively charged chloride ions to enter the neuron. This causes hyperpolarization, which makes it harder for the nerve to trigger an action potential. Strychnine blocks this process by binding to the same receptor without providing the inhibitory effect. Without the "brake" of glycine, motor neurons are easily activated by excitatory neurotransmitters. This leads to intense, spastic muscle contractions.

The biological process of creating strychnine involves many specific chemical steps. It begins with the enzyme strictosidine synthase, which catalyzes the condensation of tryptamine and secologanin. This leads to a Pictet-Spengler reaction to form strictosidine. Through various stages like hydrolysis and oxidation by a Cytochrome P450 enzyme, the molecule reaches an intermediate called the Wieland-Gumlich aldehyde. This aldehyde was first isolated by Heimberger and Scott in 1973, though it was synthesized earlier in 1932 by Wieland and Gumlich. Finally, the addition of acetyl-CoA through an aldol reaction helps form prestrychnine, which eventually becomes strychnine.

Because of its intricate structure, strychnine has long been a challenge for chemists. It contains a specific array of rings, stereocenters, and nitrogen functional groups. Sir Robert Robinson once noted that the molecule was incredibly complex for its size. In 1954, Robert Burns Woodward and his research group achieved the first total synthesis of strychnine. This was a landmark event in organic chemistry. Woodward later published a much more detailed 42-page report on this work in 1963. Since then, more than a dozen research groups have worked to achieve its stereocontrolled preparation independently.

Strychnine poisoning is extremely dangerous for humans and many animals. In adults, the minimum lethal oral dose is estimated between 30 and 120 mg. For animals, the toxicity varies; for example, the oral dose is 16 mg/kg in rats and 2 mg/kg in mice. Symptoms usually appear within 15 to 60 minutes after ingestion. Early signs include restlessness, nervousness, and muscle twitching. As the poisoning progresses, the body may experience opisthotonus, a dramatic spasm where the back and neck arch intensely.

Death often results from asphyxia caused by the paralysis of respiratory muscles.

Not all species react to the toxin in the same way. Some animals have evolved resistance to the alkaloids found in the fruit they eat, such as certain fruit bats. The drugstore beetle is also able to digest pure strychnine because it has a symbiotic gut yeast. In terms of regulation, the use of strychnine baits has changed significantly over time. In the United States, most strychnine baits were replaced by zinc phosphide baits starting in 1990. In the European Union, the use of strychnine as a rodenticide has been forbidden since 2006. This has helped prevent the accidental poisoning of non-target animals.