The analysis of pyrethrum flowers by the Seil and Wilcoxon-Holaday methods

Mitchell, Wm.; Tresadern, F. H.; Wood, Simon A.

doi:10.1039/an9487300484

Cited by 7 publications

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…O~~ and 4'7% calculated as chrysanthemum monocarboxylic acid. These recoveries presumably represented the less steam-volatile acid suggested by Mitchell et al 3 to be a hydration product of chrysanthemum monocarboxylic acid ; the results thus showed the loss typical of the Seil assay. Since this acid had already been shown to be 1 0 0 ' ) ' pure by the mercury-reduction method, and was isolated by a hydrolytic method closely similar to those used in both assay methods, it is difficult to account for the fact that the original material from which it was derived gave the same results for ' pyrethrin I ' by both methods ; this phenomenon had been already noted' with similar polymerized material extracted as such from pyrethrum.…”

mentioning

confidence: 74%

An examination of polymerized pyrethrins

Campbell¹,

Mitchell²

1950

J Sci Food Agric

View full text Add to dashboard Cite

The resinous material formed by polymerization of a highly purified pyrethrum concentrate has been examined. It was insoluble in cold light petroleum or deodorized kerosene, and gave high values for apparent pyrethrins by the Seil or mercuryreduction methods, although it was devoid of insecticidal effect on houseflies. In these respects it resembled the additional ' pyrethrins ' recently shown' to be extracted by chloroform or by warm light petroleum from pyrethrum flowefs, differing only in its higher content of apparent 'pyrethrin 1.On hydrolysis of this material, pure chrysanthemum mono-and di-carboxylic acids were isolated in yields of some 75% of the quantities calculated from the analysis. These acids were identical with those derived from normal pyrethrum extracts. Hence it appears that polymerization is confined to the keto-alcoholic constituents of the esters, the acids not being involved. The chemical assay methods at present available do not distinguish such polymerized material from true pyrethrins : but the modification described by Mitchell and Tresadernl largely prevents the extraction of polymerized material.The need for confirming all chemical assays by biolugical tests is emphasized. A portion of the monocarboxylic acid was esterified with DL-allylcyclopentenolone ; thc ester possessed the expected insecticidal activity. The action of this ester on houseflies is discussed and contrasted with that of the pyrethrins.

show abstract

mentioning

confidence: 74%

An examination of polymerized pyrethrins

Campbell¹,

Mitchell²

1950

J Sci Food Agric

View full text Add to dashboard Cite

show abstract

The analysis of pyrethrum flowers

Mitchell¹,

Tresadern²

1949

J. Chem. Technol. Biotechnol.

View full text Add to dashboard Cite

It is shown that in the assay of pyrethrum flowers the customary use of warm solvent (soxhlet) gives erroneously high results for pyrcthrin 11, especially when the higher-boiling grades of ligroin arc used. Cold exvaction gives lower results for pyrethrin 11, and largely eljminrtcs the variations in the results obtained with diffcrent grades of ligroin. It is also shown that cold ligroin extract:c all the inse:ticidally-active pyrethrics, and that the additional pyrcthrins exrncted by hot ligroin are non-toxic to house-flies. Chloroform. is"shown to extract a particularly large quantity of such non-toxic pyrcthrins." The use of cold ligroin both for the assay, and for the commercid extraction, of pyrethrum flowers is therefore recommended; and it is also suggested that the flowers should be standardized only on their content of pyrethrin I.Pyrethrum flowers are usually analysed by the Seil'. method, or, less frequently, by the mercury r e d~c t i o n~.~ method. In a recent paper (Mitchell, Tresadern and Wood)6 the accuracy of these methods was studied, using the pure chrysanthemum acids for this purpose. It was confirmed that the mercury reduction method gave satisfactory results, provided that it was carried out under carefully standardized conditions; a small modification, designed to improve the results for pyrethrin 11, was proposed. It was also confirmed that the Seil method gave low results for pyrethrin I, and it was shown that these low results were not caused by the presence of mineral acid, as had previously been supposed, but were due to D temperature effect in the steam distillation. Experiments suggested that the .apparent loss of chrysanthemum monocarboxylic acid was due, not to decarboxylation, but to direct hydration to a saturated hydroxy-acid. This latter was much less readily voIatile in steam than chrysanthemum monocarboxylic add, and was also sparingIy soIubIe in Iigroin. A modified Seil method which eliminated these low results was described. A series of comparative analyses of commercial pyrethrum extracts confirmed the accuracy of the above results; but the methods were not applied to the analysis of pyrethrum flowers.In the Seil, mercury reduction, and most of the earlier methods which have been proposed for the assay of pyrethrum flowers, the crushed drug is extracted with ligroin in a soxhlet, or other continuous extractor. In such extractors the drug is extracted with the o u~y l n solvent at a temperature just below its boiling point. In commercial extraction of the flowers, however, cold solvents are generally employed, and the yields of total pyrethrins are somewhat lower than those calculated from the laboratory assays using the soxhlet method. Thus, large-scale experiments on Kenya pyrethrum flowers, the authors have found that cold ligroin rarely extracts more than 95% of the total pyrethrins on the basis of the laboratory test (Seil, or . mercury reduction). Using old flowers, or those appearing to have been carelessly dried or stored, the yields have been only 8 0 %~ or even lo...

show abstract

The chrysanthemumcarboxylic acids. III.—Lactonization of the chrysanthemic acids

1951

View full text Add to dashboard Cite

(±)‐cis‐Chrysanthemic acid is readily lactonized in boiling dilute sulphuric acid to the crystalline (±)‐cis‐dihydrochrysanthemo‐δD‐lactone. The lactone ring is opened by alkali hydrolysis and a derivative of the (±)‐cis‐δD‐hydroxydihydrochrysanthemic acid is obtained. With methanolic sulphuric acid the lactone ring is opened to give mainly methyl (±)‐cis‐±‐methoxydihydrochrysanthemate together with methyl (±)‐cis‐chrysanthemate. In contrast, (±)‐trans‐chrysanthemic acid is converted under similar conditions into the crystalline (±)‐trans‐δ‐hydroxydihydrochrysanthemic acid. The mechanisms of these reactions and their bearing on the Seil and the Wilcoxon–Holaday methods of pyrethrum assay are discussed. On heating at 300° C. in sealed tubes (±)‐cis‐and (±)‐trans‐chrysanthemic acids and (±)‐cis‐dihydrochrysanthemo‐δ‐lactone are converted into an isomeric crystalline lactone, (±)‐pyrocin. This is shown by oxidative degradation not to be a dihydrochrysanthemo‐lactone but to be (±)‐β‐isobutenylisohexano‐σ‐lactone. These lactones are substantially non‐toxic to houseflies.

show abstract

The analysis of pyrethrum flowers by the Seil and Wilcoxon-Holaday methods

Cited by 7 publications

References 0 publications

An examination of polymerized pyrethrins

An examination of polymerized pyrethrins

The analysis of pyrethrum flowers

The chrysanthemumcarboxylic acids. III.—Lactonization of the chrysanthemic acids

Contact Info

Product

Resources

About