The known compounds that are by far the most toxic (Table 1)
1) Botulinum toxin (botulin): high molecular weight proteins from bacteria that reproduces preferentially on spoiled or inadequately preserved foods. Fortunately, this toxin cannot survive high temperatures (as in cooking, for example), so botulin-induced food poisoning is relatively rare.
2) Tetanus toxin: It is administered in an inactivated form through innoculation as protection against lockjaw and induces the formation of protective antibodies in the human immune system.
3) In the case of botulin, ca. 1.2 x 108 molecules suffice to provoke a deadly response, whereas with tetanus toxin the number is ca. 4.0 x 108, and for the much smaller snake poison b-bungarotoxin 5.7 x 1011 molecules are required. Given that a mole of a substance consists of 6.023 x 1023 molecules, these are all impressively small numbers.
1) The most poisonous low molecular weight compounds come from the sea.
2) One dinoflagellum, Gambierdiscus toxicus, produces two highly effective poisons, perhaps the most toxic of all organisms.
3) These toxins can enter the human body during the consumption of coral fish and are the source of a fish poisoning known as ciguatera that affects ca. 20000 people a year. The formidably complex natural products maitotoxin (1) and palytoxin (2), shown in Fig. 1, together with ciguatoxin itself, are all similarly constructed.
4) Maitotoxin classes not only as the most poisonous peptide but also as the highest molecular weight natural product that is not a biopolymer.
The lowest molecular weight toxins:
1) batrachotoxin (3): the poison of the Columbian arrow-poison frog; In order to isolate enough of the material to characterize it, four expeditions fought their way through the Columbian jungle over the course of eight years. The extract from 5000 frog skins finally permitted isolation of 11 mg of pure batrachotoxin.
2) tetrodotoxin (4): pufferfish
The Most Toxic Plant Poisons
1) The glycoprotein ricin, from the castor bean, displays the greatest toxicity.
2) Nicotine (5) and strychnine (6), are three orders of magnitude less toxic. The injection of nicotine present in the tobacco of a single cigar is enough to kill an adult.
3) The arrow poison curare (8), used by South American Indian tribes, seems almost harmless: two orders of magnitude less toxic than the two plant alkaloids just cited.
4) Oral toxin intake is the most common cause of poisoning by atropine (9), the poisonous substance from deadly nightshade. This especially poses a threat to small children, since they readily confuse the sweet black nightshade berries with cherries, and may die from eating as few as three or four.
The Most Toxic Synthetic Poisons
1) 2,3,7,8-Tetrachlorodibenzodioxin (dioxin, TCDD) (13): called "ultrapoison".
2) It has been "on everyone's tongue" since the tragic accident at Seveso, Italy, on July 10, 1976, when 2 kg of the substance escaped into the environment.
3) Dioxin leads to chloracne in humans and shown to be carcinogenic.
4) The disconcerting persistence of synthetic TCDD, which is not metabolized by living organisms or decomposed in sediments. Its half-life in soil is 2-9 years, and in the air up to 32 days.
5) The crop-protection agent parathion (14): a sad reputation as a suicide agent, roughly 100 times less toxic than dioxin, and relatively rapid environmental decomposition.
6) "Traditional" poisons like potassium cyanide and arsenic oxide must be taken in relatively large doses if they are to have a lethal effect.
