Toxins, Poisons, and Venoms

when we think of toxic substances, synthetic chemicals tend to come to mind. But in order to understand human-made toxic compounds, technically known as toxicants, it is helpful to first look at toxins, those toxic compounds that occur naturally. Naturally occurring toxins can be further segregated into poisons, the chemicals that enter the body via contact between host and victim, and venoms, the chemicals that are injected into the victim s body via stingers, fangs, or teeth. 

There are over 400,000 different plant species on Earth, and within them all is a dizzying array of organic chemicals. Given the number of chemicals available for consumption among plant species, it is not surprising that some plants contain chemicals that are poisonous to 

Al ui S. Kolok, Modern Poisons-. A Bri Introduction to Contemporctry Toxicolo, DOI 10.5822/ 978-1-61091-609-7 8, 2016 Alan S. Kolok. 

Unlike herbivores that often consume only a small portion of 

In nature, the art of chemical warfare may have reached its zenith with the innovation of venomous animals, those that not only contain poisonous toxins but also have the anatomical apparatus to inject those toxins directly into other animals. Venoms come in four different types cytotoxic, causing cell death proteolytic, dismantling the molecular structure around the area of the injection hemotoxic, causing failure within the cardiovascular system or neurotoxic, acting on the nervous system and the brain. 

---

West, D.J., Andrews, E.B., Bowman, D McVean, A.R., and Thorndyke, M.C. (1996) Toxins from some poisonous and venomous marine snails. Comp. Biochem. Physiol., 113C, 1-10. 

All sea snakes are poisonous and their venoms are extremely toxic. The LD q for crude sea snake venom can be as low as 0.10 fig/g mouse body weight (i). For purified toxin the LD q is even lower, suggesting the high toxicity of sea snake toxins and venoms. This toxicity is derived from the presence of potent neurotoxins. Compared to snake venoms of terrestrial origin, sea snake venoms have been studied less. Different enzymes reported to be present or absent are summarized in Table I. 

Williams, B. L., Brodie, E. D., Jr., and Brodie E. D., Ill (2004). A resistant predator and its toxic prey persistence of newt toxin leads to poisonous (not venomous) snakes. Journal of Chemical Ecology 30,1901-1919. 

Russel, F.E., Marine toxins and venomous and poisonous marine plants and animals (invertebrates), Adv. Mar Biol., 21, 59, 1984. 

B. S. Jangi, Centipede Venoms and Poisoning, In Handbook of natural toxins Insect poisons and allergens and other invertebrate venoms A. T. Tu, Ed. Dekker New York, 1984 Vol. 2, pp 333-368. 

In antiquity, natural toxins were exploited to make poison weapons to wage the earliest forms of biological and chemical warfare. A wide range of substances, from toxic plants and venomous insects and reptiles to infectious agents and noxious chemicals, were weaponized in ancient Europe, the Mediterranean, North Africa, the Middle East, Central Asia, India, China, and in the Americas. Evidence for the concept and practice of toxic warfare can be traced back thousands of years. Eor example, cuneiform tablets from about 1200 bc record that the Hittites of Asia Minor deliberately drove plague victims into enemy territory. 

A few extremely toxic and supertoxic chemicals are listed in Table 2, along with their environmental sources and toxicity targets. Some of these are toxins found in the venoms of poisonous snakes or in the tissues of certain species of animals. Dr. Findlay Russell, who has made enormous contributions to our understanding of the nature of animal toxins, their modes of biological action, and the procedures for treating people who have been envenomed or poisoned, estimates that there are about 1200 known species of poisonous or venomous marine animals, countless numbers of venomous arthropods (spiders), and about 375 species of dangerous snakes (out of a total of about 3500 species). 

Naturally occurring poisons which are also more potent than the nerve gases are found in such sources as snake venoms, among the substances known as arrow poisons, and among toxic proteins found naturally, such as ricin, the toxic protein of the castor bean, and the bacterial toxins, such as tetanus toxin and botulinum toxin. Few of these highly toxic substances appear at present to be useful per se as chemical warfare agents, but intensive research on any of them may well lead the chemist to new toxic substances with military practicality. 

The fargefs for natural biological toxins include ion channels and receptors for transmitfers. At least four parts of fhe volfage-gafed sodium charmels are binding sifes for extremely toxic natural products. " Tetrodotoxin (Fig. 30-16), which is found in the puffer fish, certain newts, and venom of fhe blue-ringed octopus, and also the shellfish poison saxitoxin (Fig. 

While there is often focus on the poisonous effects of synthetic chemicals, the most poisonous chemicals are bacterial toxins, marine toxins, fungal toxins, mycotoxins, venoms (from snakes, insects, arachnids, and other animals), and some plant toxins. Table 4.1.1.2 shows the LD50 values for toxicants including poisons and nonpoisons. This can help you judge the relative acute toxicity of a chemical, but it does not indicate chronic or long-term toxicity. Whether a substance is fatal, toxic, or harmful also depends on the dose, of course. There is also no relationship between toxicity and whether a compound is simple or complex. The mechanism of toxicity varies greatly, and structure-activity relationships are not simple (see Chemical Connection 4.1.1.1 Structure-Activity Relationships). 

Scorpion venoms secretions of the scorpion stinging apparatus. Active principles of S.v. are the neurotoxic scorpamines, which are similar to cobra toxins (see Snake venoms) with respect to M, (6,800-7,200, 4 disulfide bridges, 63-64 amino acid residues of known sequence), amino acid composition (high contents of basic and aromatic amino acids) and activity (both peripheral and central nervous system). The toxin from the North African scorpion, Androc-tonus australia, is one of the most potent known nerve poisons. 

Chapter 8 focused on natural poisons and dealt with chemicals that were directly involved in the day-to-day arms race between species. A ratdesnake s venom, for example, has to neutralize a rodent so that the snake can have dinner. Toxins such as these have to be administered via a spine or a fang or a stinger. In other cases, the poison is not delivered, but rather lies within the animal s body, and exposure only occurs when a predator eats, or attempts to eat, the poisonous prey. The tissues of the blowfish, for example, are edible but contain tetrodotoxin, and extreme care in preparation is necessary lest the diner receive a potentially lethal dose of the neurotoxin. 

The Toad Poisons.—The ugly and venomous toad owes its reputation to the presence of bufotoxin in the secretion of its skin glands. Related toxins have been obtained from other species of the animal. 

Russell, F. E. (1965) Marine toxins and venoms poisonous marine animals. Advance Marine Biol., 3,255-384. 

---