12 December 2018

Rotenone - a natural pesticide

Natural toxin

Rotenone is a broad-spectrum piscicide and insecticide used for e.g. the elimination of invasive fish in ponds and lakes and lice on domestic animals and agricultural fields

Figure 1: (Left) Lonchocarpus utilis; (right) Derris elliptica

“(…) natives collected roots of a viney shrub, Lonchocarpus sp., and threw the crushed roots into small streams and pools. The chemical in the root stunned the fish and caused them to float to the surface where they could be easily collected.”(Marrs 2012, p. 256).

According to ethnobotanical records, rotenone-containing plants historically have been used by indigenous people in tropical and subtropical countries to catch fish and as an arrow poison. It was first discovered by the industrial nations of the western world after the First World War, and its use as first a fish poison, and later insecticide, became widespread in the 20th century. Commercial rotenone has been used for eliminating unwanted fish, insects, mites, ticks, lice and spiders, and sold under names such as Cubé and Derris.

Figure 2: Rotenone (ISO) / (2R,6aS,12aS)-1,2,6,6a,12,12a-
[3,4-b]furo(2,3-h)chromen-6-one (IUPAC). Click figure
for interactive 3D model

Rotenone (Fig. 2) is found in at least 60 different, tropical and subtropical, species of Fabaceae, including the commercial sources Lonchocarpus utilis (syn. L. urucu, Deguelia utilis) and Derris elliptica, native to South America and South-east Asia respectively. It occurs mainly in roots in association with the resin ducts in phloem and xylem. Rotenone was the first rotenoid identified; rotenoids being a family of compounds similar to isoflavones, containing a cis-fused tetrahydrochromeno[3,4-b]chromene nucleus.

Rotenone is highly toxic to fish and many insects, moderately toxic to mammals and relatively harmless to plants. Its insecticidal activity is based on the inhibition of mitochondrial oxidation, more specifically: the blocking of the electron transport from complex I to ubiquinone. It may further cause interference in nerves and muscles even at low concentrations. In mammals, rotenone is metabolized by hydroxylation in the liver, where the product hydroxyrotenone has similar acute toxicity as the parent compound, while dihydroxyrotenone significantly less. Symptoms of acute mammalian poisoning include respiratory stimulation/ repression, ataxia, convulsions, tremors, vomiting and respiratory arrest. Symptoms following exposure in humans include eye irritation, dermatitis and numbness of oral mucous membranes after inhalation of powdered derris root. Exposure to the compound of humans has further been associated with (onset of) Parkinson’s disease in humans. LD50 in mammalian studies range from 25 to 3000 mg kg-1 bodyweight, depending on species and preparation. It is easily degradable by photodegradation and heat.

SMILES: CC(=C)[C@H]1Cc2c(O1)ccc3c2O[C@@H]4COc5cc(OC)c(OC)cc5[C@@H]4C3=O

References and further reading

  • Marrs, Tim. 2012. Mammalian Toxicology of Insecticides. Royal Society of Chemistry.
  • Pouchieu, Camille, Clément Piel, Camille Carles, Anne Gruber, Catherine Helmer, Séverine Tual, Elisabeth Marcotullio, Pierre Lebailly, and Isabelle Baldi. 2018. “Pesticide Use in Agriculture and Parkinson’s Disease in the AGRICAN Cohort Study.” International Journal of Epidemiology 47 (1): 299–310. https://doi.org/10.1093/ije/dyx225.
  • “Rotenone - an Overview | ScienceDirect Topics.” n.d. Accessed December 11, 2018. https://www-sciencedirect-com.ep.fjernadgang.kb.dk/topics/neuroscience/rotenone.
  • Van Andel, Tinde. 2000. “The Diverse Uses of Fish-Poison Plants in Northwest Guyana.” Economic Botany 54 (4): 500–512. https://doi.org/10.1007/BF02866548.

Picture attribution