Pyrethrin synergists

Bruce, W.N. (1967). Detector cell for measuring picogram quantities of orga no-phosphorus insecticides, pyrethrins synergists and other compounds by gas-chroinatography. A grit-, food Chem. 15. 178-181. 

Piperonyl butoxide [51-03-6] is 5-[2-(2-butoxyethoxy)ethoxy]methyl-6-propyl-l,3-benzodioxole (11) d 1.04—1.07, vp 0.13 kPa at 25°C). The rat oral LD qS are 7500, 6150 mg/kg. Piperonyl butoxide is the synergist commonly used with natural pyrethrins in aerosol sprays. 

Sesamex [51-14-9] (Sesoxane) (30) is a synergist oflow toxicity, acute oral LD q (rat) = 2000 2270 mg/kg, for pyrethrins and allethrin. 6,7-Dihydroxy 4-methylcoumarin has been offered as an antioxidant for phenoHcs and polymers, and as an anthelmintic. 2,4,5-Trihydroxybutyrophenone has been available as an antioxidant and light stabilizer for polyolefins, waxes, and foods. Isoflavones, eg (31), have been patented as components of antioxidant compositions for foods and cosmetics (qv) (97). 

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

Bates, Hewlett, and Lloyd (2) therefore studied the synergistic effects of some compounds related to 2-diethylaminoethyl 2,2-diphenyl-w-pentanoate on the insecticidal activity of pyrethrins. They found active compounds when a 2-diethylamino moiety was joined to the diphenylmethyl moiety through an ester, ketone, or ether linkage. However, none of the compounds investigated approached piperonyl butoxide in synergistic activity with pyrethrins. 

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. 

This is interesting when one considers the effect of synergists on the synthetics. All of the synthetics mentioned above are based on chrysanthemum monocarboxylic acid and in the case of allethrin, cyclethrin, and furethrin on the alcohol moiety there is only one double bond. When checked against the standard synergists, these synthetics do not show the degree of synergism shown by pyrethrins and this may be because of the fact that there is only one double bond for epoxidation, compared with two in the pyrethrolone radical, and therefore the synergist would not block this epoxidation step as effectively. 

Bioallethrin is a synthetic pyrethrin insecticide. Piperonylbutoxide, a weak insecticide itself, has synergistic activity. The same holds true for the combination of pyrethrum extract with piperonylbutoxide. These combinations have the same efficacy as permethrin. Local irritation occurs frequently effect and contact with mucous membranes and the eyes must be avoided. 

Pyrethrins affect nerve membranes by modifying the sodium and potassium channels, resulting in depolarization of the membranes. Formulations of these insecticides frequently contain the insecticide synergist piperonyl butoxide [5- 2-(2-butoxyethoxy) ethoxymethyl -6-propyl-l,3-benzodioxole], which acts to increase the efficacy of the insecticide by inhibiting the cytochrome P450 enzymes responsible for the breakdown of the insecticide. 

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) ... 

Examples of these include sesamin and sesamolin, both active principles of sesame oil, and piperonyl butoxide (PBO) and sesamex, both synthetic products. Although initially developed for use with pyrethrins, they have since been observed to synergize some, but not all, carbamates, organophosphates, pyrethroids, and organochlorines. In addition to the MDP compounds, another type of synergist called MGK 264 was developed to synergize the toxicity of pyrethroids and rotenone. The structure of piperonyl butoxide and MGK 264 are as follows ... 

The natural pyrethrin insecticides are esters derived from the alcohols cinerolone, jasmololone, and pyrethrolone (Fig. 6). Extracts of pyrethrum, the dried flowerheads of Chrysanthemum cinerariae-folium, contain a mixture of six of these ester (Fig. 6) and are commonly available with the addition of the pyrethrum synergist piperonyl butoxide. Variations on these basic structures have... 

Piperonyl butoxide, also called PBO, is a common synergist used with botanical insecticides such as pyrethrin and citrus oils. PBO is sufficiently toxic that it was recently recognized as a pesticide itself. When used frequently at high concentrations, PBO may affect the human nervous system. For this reason, many organic certification programs prohibit the use of pesticides that contain PBO... 

Precautions Pyrethrin insecticides are moderately toxic to mammals. They will kill lady beetles but do not appear to be harmful to bees. Be aware that many commercial products contain the synergist piperonyl butoxide to enhance the toxicity of the pyrethrin. (See "The Other Ingredients on page 469 for more information.)... 

Piperonyl butoxide is a synergist for carbamates, pyrethrins, pyrethroids, and rotenone. 

The pyrethrins and some pyrethroids are commonly co-formulated with the synergist, piperonyl butox-ide. This has limited toxic potential in itself but inhibits both oxidative and hydrolytic detoxification reactions and so enhances their toxicity - especially to insects. 

Pyrethrins and synthetic pyrethroids are among the safest of the topically applied ectoparasiticides, because of their selective toxicity for insects (mam-malian-to-insect toxic dose ratio is greater than 1000, compared with 33 for organophosphates and 16 for carbamate insecticides). In contrast to the very wide margin of safety for mammalian species, pyrethroids are toxic to fish. The synergistic action of pyrethrins and piperonyl butoxide (in combination preparations) is due to the inhibition by piperonyl butoxide of the microsomal enzyme system of some arthropods. Preparations of synthetic pyrethroids (permethrin, cypermethrin) often contain a mixture of drug isomers in varying proportions. 

Commercial formulations of pyrethrins usually contain piperonyl butox-ide (PO). PO is a well-known synergist that inhibits the metabolic degradation of pyrethrins and thereby intensifies the effects of the active ingredients of pyrethrins J28-29 ... 

Use Synergist in insecticides in combination with pyrethrins in oil solutions, emulsions, powders, or aerosols. 

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