Toxins make up a very widespread class of compounds, since they are found in animals, plants, and microorganisms. They are most commonly used during defensive acts against potential predators, as well as for capturing prey. Poisons, which lead to toxicity when ingested passively, should be distinguished from toxins, which are actively injected into the bodies of prey.

Poisons

Poisons are generally non-peptic compounds made by various organisms such as microscopic algae and dinoflagellates. An example would be the saxitoxin responsible for paralytic shellfish poisoning, which is seen in people who eat shellfish in which this toxin has accumulated. It has also been shown that certain fish (like the fugu puffer fish) and certain crabs are capable of accumulating tetrodotoxin, which is produced by a dinoflagellate. Certain frogs accumulate different alkaloids, like epibatidine, from their diet. Several of these molecules have proven to be very interesting pharmacological tools, and studies on them have revealed their great therapeutic potential. Epibatidine and its derivatives have demonstrated strong analgesic capacities due to their activity on nicotinic acetylcholine receptors, which intensifies the release of norepinephrine in the spinal cord.

Toxins

On the other hand, toxins are generally peptic and are found in animal venoms. They are directly linked to a venomous apparatus whose role is to inject the venom into the bodies of prey, generally by a bite, sting, or scratch.

Today, snake venom toxins are used in many areas, whether in fundamental research, as a diagnostic tool, or as a therapeutic tool. On a fundamental level, use of these types of toxins has led to great advances in different areas of biology. As an example, nerve growth factor (NGF), whose activity favours rapid multiplication of peripheral nerve fibres, was discovered in one type of cobra venom. Used for its protection of neurons, this peptide has also been examined in cell culture, and studies show that it leads to rapid growth of synapses and allows scientists to explore the mechanism behind them. The role of snake toxins does not stop at experimental biology. They also play a not insignificant role in the development of new diagnostic tools, and are used for their therapeutic properties. BotrocetinTM, an extract from the venom of Bothrops atrox, is a powerful platelet aggregant that helps diagnose several hereditary haemorrhagic conditions, like Von Willebrand disease. In this particular case, the toxin allows for a very accurate diagnosis of the type of the disease. Snake toxins also appear very promising in the field of cancer treatment. Eristostatin (from Eristicophis macmahoni) destroys melanoma metastasis cells without any direct harm to normal cells, while contortrostatin (from Agkistrodon contortrix) inhibits the adhering of cancerous cells to structural proteins, which prevents them from penetrating basement membranes and blocks them from spreading through the body.

Toxins with pharmaceutical uses are not limited to snake toxins. Spiders, scorpions, or the little-known cone snails (marine gastropods with multicoloured shells) are species that show great promise for the development of new medicines.