Pyrethrum flowers

Godin et al. (10), working on the effect of insecticidal activity of pyrethrum flowers from fresh and dried flowers, showed that extracts from fresh flowers had little or no greater effect on pyrethroid content and insecticidal activity than extracts from dried flowers with drying temperatures up to 80 °C. However, some of all the pyrethrin was lost at 120°C. The principal loss was in pyrethin I and not pyrethin II. 

Both cis- and trans-chrysanthemic nitriles and amides were resolved into highly enantiopure amides and acids by Rhodococcus sp. whole cells [85]. The overall enantioselectivity of reactions of nitriles originated from the combined effects of a higher (lJ )-selective amidase and a (IJ )-selective nitrile hydratase (Figure 6.29). Chrysanthemic acids are related to constituents of pyrethrum flowers and insecticides. 

Fujitani [6] separated the insecticidally active syrupy ester from pyrethrum flowers in 1909 and named the ester pyrethron. Yamamoto [7, 8] subjected the hydrolysis product of this pyrethron to ozone oxidation, and isolated Iram-caronic acid and aldehyde (1 and 2, respectively, Fig. 3). Although Yamamoto did not determine the structure of this acid, he presumed it to be pyrethron acid (Fig. 3). Eventually, the presence of a cyclopropane ring in the molecule of natural pyrethrins became clear for the first time in 1923. 

LaForge FB, Barthel WF (1945) Constituents of pyrethrum flowers XVIII. The structure and isomerism of pyrethrolone and cinerolone. J Org Chem 10 114-120... 

Crombie L (1995) Chemistry of pyrethrins. In Pyrethrum flowers, production, chemistry toxicology, and uses, ed by Casida JE, Quistad GB. Oxford University press, New York, Oxford, pp 124... 

Schechter MS, Green N, LaForge FB (1949) Constituents of pyrethrum flowers XXIII. Cinerolone and the synthesis of related cyclopentenolones. J Amer chem Soc 71 3165-3173... 

Elliott M (1995) Pyrethrum flowers production, chemistry, toxicology, and uses. In Casida JE, Quistad GB (eds) Chemicals in insect control. Oxford University Press, New York... 

La Forge FB, Soloway SB (1947) Constituents of pyrethrum flowers revision of the structure of dihydrocinerolone. J Am Chem Soc 69 2932-2935... 

Casida JE (1980) Pyrethrum flowers and pyrethroid insecticides. Environ Health Perspect 34 189-202... 

J.E. Casida (1973). Pyrethrum, The natural insecticide , Academic Press, New York and London. R.H. Nelson (1975). Pyrethrum Flowers, Third edition , McLaughlin Gormley King Co., Minneapolis. 

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 ... 

The most economically important group of natural plant insecticides are the pyrethrins, a group of six closely related esters extracted from pyrethrum (Chrysanthemum clnerariaefollum) flower heads (Figure 1). Pyrethrum has been used as an insecticide since at least the early 1800 s in Persia and Yugoslavia. By 1828 pyrethrum was being processed for commercial Insect control, and by 1939 imports of pyrethrum into the United States reached a peak of 13.5 million pounds. Use of the natural product declined in the early 1950 s because of the advent of synthetic pyrethroid analogs (for example, allethrins), which were both more stable and more effective in the field. The present worldwide demand for pyrethrum flowers remains in excess of 25,000 tons annually and is satisfied by the estimated 150 million flowers still hand-harvested daily, predominantly in natural stands and cultivated fields in Kenya, Tanzania, and Ecuador (9 ). 

The pyrethrins are valuable insecticidal components of pyrethrum flowers, Chrysanthemum cinerariaefolium (= Tanacetum cinerariifolium) (Compositae/Asteraceae). The flowers are harvested just before they are fully expanded, and usually processed to an extract. Pyrethrum cultivation is conducted in East Africa, especially Kenya, and more recently in Ecuador and Australia. The natural pyrethrins are used as a constituent of insect sprays for household use and as post-harvest insecticides, having a rapid action on the nervous system of insects, whilst being biodegradable and non-toxic to mammals, though they are toxic to fish and amphibians. This biodegradation, initiated by air and light, means few insects develop resistance to the pyrethrins, but it does limit the lifetime of the insecticide under normal conditions to just a few hours. 

Currently pest control by natural plant extracts is practiced primarily by subsistence farmers in those less developed part of the world where it is still an economic necessity.(ref. 3). Of the approximately 2000 plant species with known insecticidal properties (ref. 4), few have been developed commercially. These include the pyrethrins, rotenones and some of the alkaloids. Pyrethrins were the most important natural plant extracts in the early commercial insecticide formulations and were already in use in Persia and Yugoslavia during the early 1800s. By 1939 pyrethrum imports to the United States were 13-5 million lbs, declining from this peak as the synthetic analogs (e.g., the allethrins) appeared on the market. The addition of stabilizers (antioxidants) and synergists to the original pyrethrum formulations saved the natural product from commercial extinction. Currently the demand for pyrethrum flowers is still over 25,000 tons per annum—met by hand-harvested crops from Ecuador, Kenya and Tanzania (ref. 5) ... 

Sashida, Y., Nakata, H. Shimomura, H. and Kagaya, M.. Sesquiterpene lactones from Pyrethrum flowers. Phytochemistry 1983 22 1219-1222. 

The fact that nature has chosen to use a cyclopropane skeleton to design a defense mechanism for certain pyrethrum flowers against insect attack has been known since 1924, when Staudinger and Ruzicka isolated and characterised (-t-)-Jrans-chrysanthemic acid 1 from the petals of these plants [1]. The active insecticidal ingredients in these plants are in fact esters of 1, which can be easily modified and which have been commercially exploited to give birth to one of the most successful classes of biomimetic insecticides, the pyrethroids. In 1997, the market value of this class of insecticides amounted to a staggering 1.5 billion US [2],... 

There are many applications where the organic compounds are extracted from natural materials. Extraction is used for preparation of pure flavor essences from expressed oils of various citrus fruit. Pyrethrum is recovered from pyrethrum flowers by solvent extraction. A continuous saponification, glycol extraction, and splitting process for converting fat into finished soap base has been used in soap production. 

Miniaturized retention has been accomplished by using solid-phase microextraction (SPME) to collect PAHs from soil, air particulate matter and urban particulates [62,165], and pyrethrins from pyrethrum flower [165] in the fibre after quantitative extraction with superheated water [62,166]. 

If you suffer from hay fever, avoid contact with pyrethrum flowers some people have allergic reac Bons to them. Pyrethrin and related products tend to work best at the lower end of summertime temperatures and are less effective when temperatures exceed 80°E... 

Pymcanlha, 192-93 Pyrcthrin. 451,463,464.480-81 Pyrethriim. See Pyrcthrin Pyrethrum flowers, 480 Pvthium ultimum. 462... 

This is an interesting three-membered ring compound produced by pyrethrum flowers (Chapter 1). It has a carboxylic acid, an alkene, and two methyl groups on the three-membered ring. Proton... 

Other antimicrobial terpenes from the Anthemideae tribe are pyrethrins. Bioassay-directed fractionation of the organic extract of Kenyan pyrethrum flowers Chrysanthemum cinerariifolium Vissiani) resulted in the isolation of two natural pyrethrin esters, pyrethrins I and II, as the major constituents [204]. These esters elicited inhibition of the multiple drug resistant Mycobacterium tuberculosis. 

CAS 8003-34-7. C20H28O3. One of the four primary active insecticidal principles of pyrethrum flowers. It is the 3-(2-butenyl)-4-methyl-2-oxo-3-cyclopen-ten-l-yl ester of chrysanthemummonocarboxylic acid. 

CAS 8003-34-7. C21H2803. Pyrethrolone ester of chrysanthemummonocarboxylic acid. Most potent insecticidal ingredient of pyrethrum flowers. 

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