Toxiferine

Key takeaways

Toxiferine belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Toxiferine to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Toxiferine from memory before moving on to harder problems.

Reference excerpt

Toxiferine, also known as c-toxiferine I, is one of the most toxic plant alkaloids known. It is derived from several plant species, including Strychnos toxifera. Historically, it has been used as an arrow poison by indigenous peoples in South America for its neuromuscular blocking properties, allowing them to paralyze animals during hunting, but also possibly kill due to paralysis of the respiratory muscles. Toxiferine functions as an acetylcholine receptor (AChR) antagonist. The paralysis caused by toxiferine can in turn be antagonized by neostigmine. Toxiferine is the most important component in calabash curare. Curare poisons contain many different toxins with similar properties of toxiferine. The most well known component of curare is tubocurarine. The paralysis caused by toxiferine is very similar to that caused by tubocurarine, however toxiferine is ~170 times as potent. The preparation of curare poisons involves complex rituals wherein the tribes extract toxins from various plants.

History Curare was discovered in 1595, however toxiferine was only first isolated and characterized in 1941 by Wieland, Bähr and Witkop. They managed to produce only a couple micrograms of this compound as it is quite hard to isolate in large enough quantities to study. This is due to the complexity of curare as it is composed of many different alkaloids. In 1949 King was able to isolate 12 different types of toxiferines (I to XII). In 1951 some of these toxiferine types were analyzed for their toxicological and pharmacological properties. These types were found to differ slightly in structure and their potency. Curares like tubocurarine were later used as anesthetics in medical procedures, but were replaced in the 1960s by synthetic curare-like drugs like alcuronium, pancuronium, atracurium and vecuronium. These drugs were safer to use as they had a shorter duration of action and less side effects. After the replacement of curares by these synthetic alternatives, research on toxiferine declined as it was hard to isolate from calabash curare and better alternatives to curares had been found thus decreasing the interest in researching this specific compound. However, curares as a whole have been (and still are) extensively researched.

Use/purpose Toxiferine is most commonly known for its use as an arrow poison alongside other curares by south american tribes. It is extracted from plants, like strychnos toxifera and chondrodendron tomentosum. It is hard to extract in large quantities. It is very toxic however, so small quantities will suffice in paralyzing or killing animals while hunting. It could be used as an anesthetic in medical procedures, however it has a very long duration of action which doesn't make it suitable for such procedures. It is also unstable in solution, which further prevents its use in medical settings. Synthetic alternatives like alcuronium can and are still used in anesthetics due to their relatively shorter duration of action and fewer side effects.

Efficacy Toxiferine is especially useful as an arrow poison because of its very minimal absorption through oral ingestion. Which is why it is safe to eat the animal after it has been shot with an arrow covered in toxiferine. It is also believed that because of its activity as muscle paralyzer, it can retain glycogen and ATP from releasing after death and by this delay rigor mortis. This makes the meat more tender for longer and maintains its flavor.

Mechanism of action Toxiferine I competes with acetylcholine, a neurotransmitter, for binding to the nicotinic acetylcholine receptors on the post-synaptic membrane of the neuromuscular junction. By binding to these receptors, toxiferine I prevents acetylcholine from attaching to them. This inhibition blocks the ion channels associated with these receptors from opening, thereby preventing the influx of sodium ions into the muscle cell. The prevention of sodium influx leads to an inhibition of depolarization of the post-synaptic membrane, which is a necessary step for muscle contraction. Without depolarization, the muscle fiber cannot generate an action potential, resulting in muscle paralysis. Toxiferine I is a potent antagonist for several acetylcholine receptors, but especially potent for muscle-type nAChR:

Binding Similar to alcuronium, toxiferine is classified as a non-depolarizing neuromuscular-blocking drug. These are drugs that inhibit signal transduction by competitive inhibition of in this case mainly muscle-type nAChRs. Toxiferine though binds 17 times stronger to muscle-type nAChRs than its pharmacological analogue alcuronium. The quaternary ammonium salt that toxiferine and its analogues share with acetylcholine is thought to be the reason for the binding affinity to the AChRs. The exact reason for the especially high binding affinity of toxiferine to for example muscle-type nAChRs is unknown. There have been attempts at understanding the exact binding of toxiferine in nAChRs, but the models are dated.

Reversing the mechanism Neostigmine is known to be effective at reversing the competitive inhibition of toxiferine and its analogues. Neostigmine works by inhibiting acetylcholinesterase, increasing the acetylcholine concentrations so it can compete more with the non-depolarizing neuromuscular-blocking drug. By this toxiferine can be freed into the circulation for excretion.

Chemistry

Structure Toxiferine I is an indole alkaloid derived from tryptamine. It has a dimeric structure with each monomer containing a quaternary ammonium salt. The parent structure, without counter ions, has the molecular formula C40H46N4O22+, while the dichloride salt has the molecular formula C40H46N4O2Cl2. Alkaloids are naturally occurring compounds that are basic and contain at least one nitrogen atom. Toxiferine is classified as a dimeric bisindole alkaloid because it is symmetrically constructed from two identical monomeric units, each containing an indole ring.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Toxiferine

Start with the simplest possible case. Write down what Toxiferine claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Toxiferine before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Toxiferine ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Toxiferine

In research: Toxiferine appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Toxiferine in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Toxiferine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dimers (chemistry), Eight-membered rings, Indole alkaloids, so understanding it makes those chapters shorter.
In everyday life: Look for Toxiferine outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Toxiferine in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Toxiferine means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Toxiferine out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Toxiferine in simple terms?

Toxiferine, also known as c-toxiferine I, is one of the most toxic plant alkaloids known. It is derived from several plant species, including Strychnos toxifera.

Why does Toxiferine matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Toxiferine?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Toxiferine.