Sodium fluoroacetate, also known as compound 1080, is an organofluorine chemical compound with the formula FCH2CO2Na. This colourless salt has a taste similar to that of sodium chloride and is used as a rodenticide.
History and production
The effectiveness of sodium fluoroacetate as a rodenticide was reported in 1942. The name "1080" refers to the catalogue number of the poison, which became its brand name.
The salt is synthesized by treating sodium chloroacetate with potassium fluoride.
Both sodium and potassium salts are derivatives of fluoroacetic acid.
Natural occurrence
Fluoroacetate occurs naturally in at least 40 plants in Australia, Brazil, and Africa. It is one of only five known organic fluorine-containing natural products.
Fluoroacetate occurrence in Gastrolobium species
Gastrolobium is a genus of flowering plants in the family Fabaceae. This genus consists of over 100 species, and all but two are native to the southwest region of Western Australia, where they are known as "poison peas". Gastrolobium growing in southwestern Australia concentrate fluoroacetate from low-fluoride soils. Brush-tailed possums, bush rats, and western grey kangaroos native to this region are capable of safely eating plants containing fluoroacetate, but livestock and introduced species from elsewhere in Australia are highly susceptible to the poison, as are species introduced from outside Australia, such as the red fox. The fact that many Gastrolobium species also have high secondary toxicity to non-native carnivores is thought to have limited the ability of cats to establish populations in locations where the plants form a major part of the understorey vegetation.
The presence of Gastrolobium species in Western Australia has often forced farmers to 'scalp' their land, that is, remove the top soil and any poison pea seed which it may contain, and replace it with a new poison pea-free top soil sourced from elsewhere in which to sow crops. Similarly, after bushfires in north-western Queensland, cattlemen have to move livestock before the poisonous Gastrolobium grandiflorum emerges from the ashes.
The related compound occurs naturally as a defensive compound in at least 40 plant species in Australia, New Zealand, Brazil, and Africa. It was first identified in Dichapetalum cymosum, commonly known as gifblaar or poison leaf, by Marais in 1944. As early as 1904, colonists in Sierra Leone used extracts of Chailletia toxicaria, which also contains fluoroacetic acid or its salts, to poison rats. Several native Australian plant genera contain the toxin, including Gastrolobium, Gompholobium, Oxylobium, Nemcia, and Acacia. New Zealand's native Puha contains 1080 in very low concentrations.
Toxicology
Sodium fluoroacetate is toxic to all obligate aerobic organisms, and highly toxic to mammals and insects. The oral dose of sodium fluoroacetate sufficient to be lethal in humans is 2–10 mg/kg.
The toxicity varies with species. The New Zealand Food Safety Authority established lethal doses for a number of species. Dogs, cats, and pigs appear to be most susceptible to poisoning.
The enzyme fluoroacetate dehalogenase has been discovered in a soil bacterium, which can detoxify fluoroacetate in the surrounding medium.
Mechanism of action
Fluoroacetate is structurally similar to acetate, which has a pivotal role in cellular metabolism. This similarity is the basis of the toxicity of fluoroacetate. Two related mechanisms for its toxicity have been discussed, with both beginning with the conversion of fluoroacetate to 2-fluorocitrate. 2-Fluorocitrate arises by condensation with oxaloacetate with fluoroacetyl coenzyme A, catalyzed by citrate synthase. Fluorocitrate binds very tightly to aconitase, thereby halting the citric acid cycle. This inhibition results in an accumulation of citrate in the blood. Citrate and fluorocitrate are allosteric inhibitors of phosphofructokinase-1 (PFK-1), a key enzyme in glycolysis. When PFK-1 is inhibited, cells are no longer able to metabolize carbohydrates, depriving them of energy. Alternatively, fluorocitrate interferes with citrate transport in the mitochondria.