| 释义 |
pyrethrin|paɪˈriːθrɪn|
[a. G. pyrethrin (Staudinger & Ruzicka 1924, in Helvetica Chimica Acta VII. 181): see pyrethrum and -in1.]
Any of a class of insecticidal terpenoid esters which are obtained from flower heads of Chrysanthemum cinerariæfolium and related species, or have been synthesized; spec. either of two such compounds (pyrethrins i and ii) which are the major active principles of pyrethrum powder.
1924Chem. Abstr. XVIII. 1819 A mixt. of the semicarbazones..of pyrethrin I..and pyrethrin II. Ibid. 2135 Myrcene and N2CHCO2Et give 31% of an acid, C12H18O2, which yields a very slightly active pyrethrin. 1934Discovery Sept. 251/2 Although the difference between pyrethrin I and II is of chemical and biological importance, their action is sufficiently similar for it to be disregarded in practical work. 1951H. H. Shepard Chem. & Action Insecticides viii. 146 The pyrethrin content is higher in flowers produced in cool mountain valleys than where the mean temperature is high. Ibid. 150 The pyrethrins and cinerins, together referred to generally as pyrethrins, are chemically unstable. 1971Inside Kenya Today Mar. 43/2 Pyrethrin-based insecticides have proved patently safe. 1971Nature 15 Oct. 441/1 Six esters are found in the pyrethrum of which the most important and plentiful are known as pyrethrins I and II. |