The pyrethrins are a pair of natural organic compounds that have potent insecticidal activity. Pyrethrin I and pyrethrin II are structurally related esters with a cyclopropane core. ["Merck Index", Eleventh Edition, 7978.] [McGraw-Hill Ryerson Chemistry 12 p.99 Michael Townsend] They differ by the oxidation state of one carbon. They are viscous liquids that oxidize to become inactivated. They are non-persistent, being biodegradable, and break down on exposure to light or oxygen. The chemical structure of pyrethrins is the basis for a variety of synthetic insecticides called pyrethroids such as permethrin and cypermethrin.

The pyrethrins are contained in the seed cases of the perennial plant pyrethrum ("Chrysanthemum cinerariaefolium"), which is grown commercially to supply the insecticide. Although extracts of the plant were already used as insecticide, the structure was first published by Hermann Staudinger and Lavoslav Ružička in 1924. [cite journal
author = Staudinger, H. und Ruzicka, L.
title = Über die wirksamen Bestandteile des dalmatinischen Insektenpulvers
journal = Helv chim acta.
volume = 7
year = 1924
pages = 177
doi = 10.1002/hlca.19240070124
] Pyrethrins are neurotoxins that attack the nervous systems of all insects. When present in amounts not fatal to insects, they still appear to have an insect repellent effect. Pyrethrins are gradually replacing organophosphates and organochlorides as the pesticide of first choice.

Pyrethrins are harmful to fish, birds, and mammals, including humans. In humans, pyrethrin irritates the eyes, skin, and respiratory systems, and it may cause other harmful effects. One study suggested a link between maternal pyrethrin use and autism in children. [ [ Insecticides in pet shampoo may trigger autism.] , New Scientist] The study indicated that mothers of autistic children were twice as likely to have washed a pet dog with a flea shampoo containing pyrethrin while they were pregnant.


External links

* [ Pyrethrins and Pyrethroids Fact Sheet - National Pesticide Information Center]
* [ Pyrethrins and pyrethroids on the EXTOXNET]

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  • Pyrethrin — Pyr eth*rin, n. [NL. Pyrethrum, generic name of feverfew, Gr. ? feverfew.] (Chem.) A substance resembling, and isomeric with, ordinary camphor, and extracted from the essential oil of feverfew; called also {Pyrethrum camphor}. [1913 Webster] …   The Collaborative International Dictionary of English

  • Pyrethrin — Pyrethrin, angeblich ein eigenthümlicher Stoff in der Bertramwurzel …   Pierer's Universal-Lexikon

  • pyrethrin — [pī reth′rin, pīrē′thrin] n. [< PYRETHRUM + IN1] either of two liquid esters, C21H28O3 or C22H28O5, derived from chrysanthemums: the active ingredient of pyrethrum …   English World dictionary

  • Pyrethrin — Strukturformel siehe unter Zusammensetzung Allgemeines Name Pyrethrine Summenformel keine, da Stoffgruppe CAS Nummer 8003 34 7 Kurzbeschreibung …   Deutsch Wikipedia

  • pyrethrin — /puy ree thrin, reth rin/, n. Chem. 1. Also called pyrethrin I. a viscous, water insoluble liquid, C21H28O3, extracted from pyrethrum flowers, used as an insecticide. 2. Also called pyrethrin II. a like compound, C22H28O5, obtained and used… …   Universalium

  • pyrethrin — py·re·thrin pī rē thrən, reth rən n either of two oily liquid esters C21H28O3 and C22H28O5 that have insecticidal properties and are the active components of pyrethrum * * * py·reth·rin (pi rethґrin) either of two esters, pyrethrin I and… …   Medical dictionary

  • pyrethrin — /paɪˈriθrən/ (say puy reethruhn) noun either of two compounds, C21H28O3 (pyrethrin 1), or C22H28O5 (pyrethrin 2), which are obtained from pyrethrum flowers and are used as contact insecticides. {pyrethr(um) + in2} …   Australian English dictionary

  • pyrethrin — noun Etymology: International Scientific Vocabulary, from Latin pyrethrum Date: 1871 either of two oily liquid esters C21H28O3 and C22H28O5 having insecticidal properties and occurring especially in the flowers of pyrethrum …   New Collegiate Dictionary

  • pyrethrin — noun Any of a number of naturally occurring insecticides extracted from the pyrethrum plant; unusual in having a cyclopropane ring …   Wiktionary

  • Pyrethrin — Py|re|th|rin [nlat. Pyrethrum (↑ Pyro ), heute: Chrysanthemum = Wucherblumenart (Bot.); ↑ in (3)], das; s, e: ↑ Pyrethroid …   Universal-Lexikon

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