Chemistry of the natural pyrethrins.

Abstract

The flowers of the herbaceous perennial Chrysanthemum cinerariaefolium Vis. (synonym, Pyrethrum cinerariaefolium Trev.), a member of the Compositae family, are valued for their insecticidal properties: the history of their employment has been discussed by Gnadinger (77,78). Commercial supplies were originally obtained from Dalmatia and Japan, but to-day the principal world source is Kenya where a rationally administered industry provides standardised products. Other Compositae flowers have insecticidal activity but of these only Chrysanthemum coccineum Willd. (synonyms, C. carneum Steud and C. roseum Adam) has commercial value, though it is cultivated on a restricted scale. The active insecticidal principles, the Pyrethrins, are contained mostly in the achenes of C. cinerariaefolium (19–21). Harvesting the crop requires much hand labour as maximum yields are obtained by gathering the flower (Fig. I) when four or five rows of disc florets are open. The flowers are artificially dried and baled and are known commercially as “pyrethrum”. As insecticides, the Pyrethrins have the advantage of low mammalian toxicity and so far insects have not easily developed resistance towards them. They are also well known for their rapid “knock-down” or paralytic properties which are valuable in dealing with flying insects.KeywordsFood AgricInsecticidal ActivityAbsolute ConfigurationDisplacement ChromatographyCyclopropane RingThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.