pyrethrin

thumb|:en:Skeletal structure|Chemical structure of some pyrethrins: pyrethrin I (R=CH3), pyrethrin II (R=CO2CH3)

The pyrethrins are a class of organic compounds normally derived from Chrysanthemum cinerariifolium that have potent insecticidal activity by targeting the nervous systems of insects. Pyrethrin naturally occurs in chrysanthemum flowers and is often considered an organic insecticide when it is not combined with piperonyl butoxide or other synthetic adjuvants. Their insecticidal and insect-repellent properties have been known and used for thousands of years.