Cinerins

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) ... 

Jasmolin II in pure form was nearly equal to cinerin II in toxicity to houseflies but much less when synergized. The synergistic factor of the synergized compounds is pyrethrum extract 9.6 jasmolin II, 7.0 cinerin II, 12.0. 

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. 

Synergist Extract Pyrethrin 1 Pyrethrin II Cinerin l Cinerin II... 

The detection of microgram quantities of pyrethrins, cinerins, keto alcohols, and chrysanthemum acids by paper chromatography and by application of these techniques to a study of possible metabolites enabled certain tentative conclusions that imply hydrolysis in insects of a large portion of the radioactive pyrethrins and synergists to corresponding keto alcohols and chrysanthemum acids. 

Clyde Kearns (personal communication) suggests that the first step in the possible detoxification of pyrethrins, including the cinerins as well as the pyrethrins, is the epoxidation of the double bond. 

Figure 6. Infrared spectrum of cinerin II Collected from gas chromatograph after isolation from silicic acid-acetonitrile-hexane partition column...

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... 

IV as a cinerin-type compound, peak V as cinerin II, and peak VI as pyrethrin II. It is evident that peak IV also contains another component. The peaks beyond peak VI are known to be of the pyrethrin type as they respond to the color test. This gas chromatography pattern was obtained with a 6-foot lA -inch column packed with 20% SE-30 on 40-60-mesh Chromosorb P. Later work provided good resolution of the peaks with a 2-foot 4-inch column packed with 20% Dow-11 silicone oil on 45-60-mesh Chromosorb P. 

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]. 

Chromatography of Pyrethrins Concentrate. Five hundred milligrams of concentrate consisting mainly of the two pyrethrins and the two cinerins were dissolved... 

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. 

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