Rotenone

Rotenone is a chemical that is used as a broad-spectrum insecticide, piscicide, and pesticide. It occurs naturally in the roots and stems of several plants. It causes Parkinson's disease if injected into rats.

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Chemistry

Rotenone has chemical formula C₂₃H₂₂O₆ and belongs to the isoflavones. It consists of colorless-to-red, odorless crystals that are soluble in ether and acetone.

Uses

Rotenone is used in solution as a pesticide and insecticide.

It is commonly used in powdered or emulsified liquid form in fisheries management to remove unwanted fish species^[1] (such as to eradicate exotic fish from their non-native habitats). People have been known to catch fish by extracting rotenone from plants and releasing it into water. The fish then come to the surface, gasping for air, and are easily caught. The initial such usage was by various indigenous tribes^[2] who simply smashed the roots.

Rotenone is also used in powdered form to reduce parasitic mites on chickens and other fowl.

Method of action

Rotenone works by interfering with the electron transport chain in mitochondria. Specifically, it inhibits the transfer of electrons from Fe-S centers in Complex I to ubiquinone. This prevents NADH from being converted into usable cellular energy (ATP).

Presence in plants

Rotenone is produced by extraction from the roots and stems of several tropical and subtropical plant species, especially those belonging to the genus Lonchocarpus or Derris.

Some of the plants containing rotenone:

• Hoary Pea or Goat’s Rue and Jicama plant(Tephrosia virginiana) - North America
• Cubé Plant or Lancepod (Lonchocarpus utilis) - South America^[3]
  • The root extract is referred to as Cubé resin
• Barbasco (Lonchocarpus urucu) - South America^[3]
  • The root extract is referred to as Cubé resin
• Tuba Plant (Derris elliptica) - southeast Asia & southwest Pacific islands
  • The root extract is referred to as Derris or Derris root
• Jewel Vine (Derris involuta) - southeast Asia & southwest Pacific islands
• Among the Mizo tribes of India (Derris walchii/D. thyrsiflora) the tender root is eaten as vegetable
  • The root extract is referred to as Derris or Derris root
• Duboisia - This shrub grows in Australia and bears white clusters of flowers and berry like fruit. The crushed plants were used by the Aboriginals for poisoning fish for food.

Toxicity

Rotenone is classified by the World Health Organization as moderately hazardous.^[4] It is mildly toxic to humans and other mammals, but extremely toxic to insects and aquatic life including fish. This higher toxicity in fish and insects is due to the fact that the lipophilic rotenone is easily taken up through the gills or trachea, but not as easily through the skin or through the gastrointestinal tract.

The lowest lethal dose for a child is 143 mg/kg. Human deaths attributed to Rotenone are rare because its irritating action causes vomiting.^[5] Deliberate ingestion of rotenone can be fatal.^[6]

The compound breaks down when exposed to sunlight and usually has a short lifetime of six days in the environment.^[7] In water rotenone may last six months.^{[citation needed]}

Rotenone is classified by the USDA National Organic Program as a nonsynthetic and is allowed to be used to grow "organic" produce.^[8]

Parkinson's disease

In 2000 it was reported that injecting rotenone into rats causes symptoms of Parkinson's disease to develop. Rotenone was continuously applied over a period of five weeks, mixed with DMSO and PEG to enhance tissue penetration, and injected into the jugular vein.^[9]

The study does not directly suggest that rotenone exposure is responsible for Parkinson's disease in humans but is consistent with the belief that chronic exposure to environmental toxins increases the likelihood of the disease.^[10]

In addition, studies with primary cultures of rat neurons and microglia have shown low doses of rotenone (below 10 nM) to induce oxidative damage and death of dopaminergic neurons^[11] and it is these neurons in the substantia nigra that die in Parkinson's disease.

It had been known earlier that the neurotoxin MPTP causes Parkinson's disease (in humans and other primates, though not in rats) by interfering with Complex I in the electron transport chain and killing dopaminergic neurons in the substantia nigra. Because of this, rotenone was investigated as a possible Parkinson-causing agent. Both MPTP and rotenone are lipophilic and can cross the blood-brain barrier.

References

1. ^ Peter Fimrite (2007-10-02). Lake poisoning seems to have worked to kill invasive pike. San Francisco Chronicle.
2. ^ National Toxicology Program - Rotenone at ntp.niehs.nih.gov
3. ^ ^{a b} Fang N, Casida J (1999). "Cubé resin insecticide: identification and biological activity of 29 rotenoid constituents". J Agric Food Chem 47 (5): 2130-6. PMID 10552508.
4. ^ (2007) The WHO Recommended Classification of Pesticides by Hazard. World Health Organization. ISBN 92-4-154663-8. Retrieved on 2007-12-02. 
5. ^ Factsheet - Rotenone
6. ^ Wood D, Alsahaf H, Streete P, Dargan P, Jones A (2005). "Fatality after deliberate ingestion of the pesticide rotenone: a case report". Crit Care 9 (3): R280-4. PMID 15987402.
7. ^ Vitax Safety Data Sheet for Derris dust, revised October 1998
8. ^ Rotenone. Resource Guide for Organic and Disease Management. Cornell University.
9. ^ Caboni P, Sherer T, Zhang N, Taylor G, Na H, Greenamyre J, Casida J (2004). "Rotenone, deguelin, their metabolites, and the rat model of Parkinson's disease". Chem Res Toxicol 17 (11): 1540-8. PMID 15540952.
10. ^ Summary of the article by Dr. Greenamyre on pesticides and Parkinson's Disease at ninds.nih.gov
11. ^ Gao HM, Liu B, Hong JS (2003). "Critical role for microglial NADPH oxidase in rotenone-induced degeneration of dopaminergic neurons". The Journal of Neuroscience 23 (15): 6181-7. PMID 12915048.

See also

• NADH dehydrogenase