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=Pyrethrin Article Outline=

The pyrethrins are a pair of natural organic compounds normally derived from Chrysanthemum cinerariifolium that have potent insecticidal activity, attacking the nervous systems of insects. Pyrethrins are gradually replacing organophosphates and organochlorides as the pesticide of choice, since organochlorides have been shown to have significant and persistent toxic effects to humans. Because they are biodegradable compounds, pyrethrins are being phased out in favor of pyrethroids, a group of synthetic analogues of pyrethrin, for insecticide uses, and appear to have an insect repellent effect when present in non-fatal doses.

History
The pyrethrins occur in the seed cases of the perennial plant pyrethrum (Chrysanthemum cinerariaefolium), which has long been grown commercially to supply the insecticide. Pyrethrins have been used as an insecticide for thousands of years. It is believed that the Chinese crushed Chrysanthemum plants and used the powder as an insecticide as early as 1000 BCE. Pyrethrins were identified as the potent chemical in the Chrysanthemum plants responsible for the insecticide properties in the crushed flowers around 1800 in Asia. Since then, the plant has been commercialized to it's wide usage now.

Well after their use as insecticides, their chemical structures were determined by Hermann Staudinger and Lavoslav Ružička in 1924. Pyrethrin I and pyrethrin II are structurally related esters with a cyclopropane core. Pyrethrin I is a derivative of (+)-trans-chrysanthemic acid. Pyrethrin II is closely related, but one methyl group is oxidized to a carboxymethyl group, the resulting core being called pyrethric acid. Knowledge of their structures opened the way for the production of synthetic analogues, which are called pyrethroids. In terms of their biosynthesis, pyrethrins are classified as terpenoids, being derived from dimethylallyl pyrophosphate, which combine by the action of the enzyme chrysanthemyl diphosphate synthase.
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Production
elaborate on process of production

Environmental Effects
- related to cut flower industry in Kenya, environmental and social issues