Cinerin I

Pyrethrins are a group of naturally occurring insecticidal substances found in the flowers of various plants of the chrysanthemum family. The following is the structure of a typical pyrethrin, cinerin I (exclusive of stereochemistry) ... 

Sawicki et al. (33) prepared by reconstitution pure samples of pyrethrins I and II and cinerins I and II and compared the toxicity of these esters with the regular pyrethrum extract on houseflies 5 to 6 days old. 

Figure 8. Infrared spectrum of a cinerin I type Fraction isolated from Celite-acetonitrile-hexane partition column and rechromatographed on a silicic acid-nitrome-thane-hexane (with 5% acetone) partition column.

The columns labeled PI reflect the total of pyrethrin I and cinerin I just as in the AO AC procedure. The gas chromatographic results are in terms of the total amount of the mixture but were analyzed as the methyl ester of chrysanthemic acid. The present state of the determination of PII (pyrethrin II plus cinerin II) is not complete because of the erratic extractability of the dicarboxylic acids from the hydrolysis mixture. The gas chromatographic pattern is distinct and straightforward. As the extraction procedure for PII is improved, the gas chromatographic method will be more applicable. The present recovery of PII is in the range of 80 to 90%. The average of the values shown in Table II for PI is 98.0%. 

Figure 1 presents the gas chromatographic responses obtained from a pyrethrum concentrate. Peak I has been identified as cinerin I, peak II as a cinerin-type compound, peak III as pyrethrin I, peak... 

STAHL, for instance, was able to demonstrate that on irradiation with long-wavelength UV light the naturally occurring contact insecticides pyrethrin I and II, cinerin I and II and jasmolin I and II present in Chrysanthemum cinerariifolium are converted to inactive pyrethrin oxides by the incorporation of oxygen [7]. 

As described in the section on Cross-resistance in this chapter, it was found that some insect species showed extremely low cross-resistance to three ingredients, pyrethrins as well as d-allethrin and prallethrin, although they developed resistance to photostable synthetic pyrethroids. The latter two compounds of d-allethrin and prallethrin have quite similar chemical structures and the same configuration as cinerin I (an ingredient of pyrethrins). It is considered preferable to develop pyrethroids retaining the characteristics of natural pyrethrins and household insecticides containing them in the perspectives of safety and low cross-resistance. 

Figure 7 shows the course of development of various synthetic pyrethroids developed by retaining chrysanthemic acid as the acid moiety and modifying the alcohol moiety. Numerous useful compounds with favorable characteristics have been derived from the structural modification of natural cinerin I (7). These underlined compounds have been put into practical use as active ingredients, mainly for household insecticides. 

Allethrin, the first synthetic pyrethroid, is a compound which is the closest in structure to cinerin I. Pyrethroids developed subsequently are mostly esters of chrysanthemic acid, and cinerin II analogs, i.e., esters of chrysanthemum acid have not been industrialized. 

Synonyms Pyrethrin I or II Cinerin I or II Jasmolin I or II. Note Pyrethrum flowers yield pyrethrum extract, of which the insecticidal constituents are collectively the pyrethrins or the natural pyrethrins ... 

Pyrethrins and pyrethroids are probably the best known and safest classes of natural or synthetic insecticides, widely used in domestic and agricultural applications (1-7). Pyrethrins are natural insecticides derived from the Chrysanthemum cineraria flowers the plant extract, called pyrethrum, is a mixture of six isomers (pyrethrin I and II, cinerin I and II, jasmolin I and II) which was first used in China in the century AD, during the Chou Dinasty. The world pyrethrum market is worth half a billion US dollars [main producers are East Africa highlands (Kenia, Tanzania and Rwanda) and Australia] however, its availability is subject to cyclical trends, due to rains and relations with farmers, who face high harvest costs also due to the fact that the flowers have to be... 

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