Non-ester Pyrethroids Research Articles

Resistance Status and Resistance Mechanisms in a Strain of Aedes aegypti (Diptera: Culicidae) From Puerto Rico.

Puerto Rico (PR) has a long history of vector-borne disease and insecticide-resistant Aedes aegypti (L.). Defining contributing mechanisms behind phenotypic resistance is critical for effective vector control intervention. However, previous studies from PR have each focused on only one mechanism of pyrethroid resistance. This study examines the contribution of P450-mediated enzymatic detoxification and sodium channel target site changes to the overall resistance phenotype of Ae. aegypti collected from San Juan, PR, in 2012. Screening of a panel of toxicants found broad resistance relative to the lab susceptible Orlando (ORL1952) strain. We identified significant resistance to representative Type I, Type II, and nonester pyrethroids, a sodium channel blocker, and a sodium channel blocking inhibitor, all of which interact with the sodium channel. Testing of fipronil, a chloride channel agonist, also showed low but significant levels of resistance. In contrast, the PR and ORL1952 strains were equally susceptible to chlorfenapyr, which has been suggested as an alternative public health insecticide. Molecular characterization of the strain indicated that two common sodium channel mutations were fixed in the population. Topical bioassay with piperonyl butoxide (PBO) indicated cytochrome P450-mediated detoxification accounts for approximately half of the resistance profile. Transcript expression screening of cytochrome P450s and glutathione-S-transferases identified the presence of overexpressed transcripts. This study of Puerto Rican Ae. aegypti with significant contributions from both genetic changes and enzymatic detoxification highlights the necessity of monitoring for resistance but also defining the multiple resistance mechanisms to inform effective mosquito control.

Analysis of Synthetic Pyrethroids by Gas Chromatography–Mass Spectrometry

The paper explains why we get many peaks during gas–liquid chromatography (GC) and attempts to rationalize the complicated GC spectra by identifying the major fragments of synthetic pyrethroids. In the present research, gas chromatography conditions in the electronic ionization (EI) mode were established that served as a benchmark in the development of a chemical ionization (CI) protocol for the selected ester and non-ester synthetic pyrethroids. CI technique is a lower energy process than EI. The lower energy yields less fragmentation, and usually a simpler spectrum with identifiable molecular ion. Common major peak in case of cypermethrin, deltamethrin, fenvalerate, and fenpropathrin was due to meta-phenoxybenzaldehyde moiety at m/z 208 (C14H10NO)+ ion. Etofenprox after protonation of ether oxygen loses one molecule of water producing m/z 359 instead of m/z 377 and it further fragmented to m/z 177 (C12 H17O)+ and 135 (C9H11O)+ ions. Above 70 % recoveries of all the pyrethroids at 0.1 and 1 μg ml−1 levels were achieved from environmental samples. Improving analytical sensitivity and selectivity is important for quantifying trace pyrethroids in matrices. In EI mode, selecting base ion for single ion monitoring or using a precursor ion for MS/MS analysis, the lower limits of quantification (less than 0.1 ppm) become possible for the analysis of synthetic pyrethroids in water.

The Joint Toxicity of Type I, II, and Nonester Pyrethroid Insecticides

Evidence suggests that there are separate binding domains for type I and II pyrethroid insecticides on the voltage gated sodium channel of the nerve cell axon, but there are no studies that have examined the mixture toxicity of nonester pyrethroids and type I and II pyrethroids. Therefore, we examined the effect of nonester pyrethroid (etofenprox), type I (permethrin), and type II (cypermethrin) pyrethroid insecticides alone and in all combinations to Drosophila melanogaster Meigen. The combination of permethrin + etofenprox and permethrin + cypermethrin demonstrated antagonistic toxicity, while the combination of cypermethrin + etofenprox demonstrated synergistic toxicity. The mixture ofpermethrin + cypermethrin + etofenprox demonstrated additive toxicity. The toxicity of permethrin + cypermethrin was significantly lower than the toxicity of cypermethrin alone, but the combination was not significantly different from permethrin alone. The toxicity of permethrin + cypermethrin + etofenprox was significantly greater than the toxicity of both permethrin and etofenprox alone, but it was significantly lower than cypermethrin alone. The mixture of permethrin and etofenprox was significantly less toxic than permethrin. The explanation for the decreased toxicity observed is most likely because of the competitive binding at the voltage-gated sodium channel, which is supported by physiological and biochemical studies of pyrethroids. Our results demonstrate that the assumption that the mixture toxicity of pyrethroids would be additive is not adequate for modeling the mixture toxicity of pyrethroids to insects.

ChemInform Abstract: Synthesis of Non-Ester Pyrethroids Having a 1-Fluoro-1-methylethyl Group Using 1,2-Migration of an Aryl Group.

When 1,4-diaryl-4-methyl-1,3-pentanediol was treated with diethylaminosulfur trifluoride to introduce fluorine atoms into the central link, 1,2-aryl group migration products which have a 1-fluoro-1-methylethyl group were obtained as two diastereomers. Utilizing this migration, some non-ester pyrethroids possessing a 1-fluoro-1-methylethyl group were prepared. The reactivity of other fluorinating reagents is also discussed.

The pyrethrins and related compounds. Part XLII:Structure-activity relationships in fluoro-olefin non-ester pyrethroids

A series of compounds containing fluorine atoms in place of hydrogen in olefinic non-ester pyrethroids has been synthesised using a route based on novel intermediates, ie 2-fluoroallyl acetates, which are coupled with aryl Grignard reagents, and tested against several insect species. In most cases, after introduction of fluorine at the olefinic position, the activity remains high in both the 1-aryl-1-(3-arylprop-2-enyl)cyclopropane and the (1-aryl-4-arylbut-2-enyl)cyclopropane series. In particular, the former series have potential as soil insecticides, because in tests against Diabrotica balteata, activities were high, and dose-transferability factors were increased by the introduction of fluorine. © 1999 Society of Chemical Industry

The pyrethrins and related compounds. Part XLII:Structure-activity relationships in fluoro-olefin non-ester pyrethroids

The pyrethrins and related compounds. Part XLII:Structure-activity relationships in fluoro-olefin non-ester pyrethroids

An Umpolung approach to fluorinated non-ester pyrethroids

An Umpolung approach to fluorinated non-ester pyrethroids

The Pyrethrins and Related Compounds. Part XLI. Structure-Activity Relationships in Non-ester Pyrethroids against Resistant Strains of Housefly (Musca domesticaL.)

A series of pyrethroids, related to NRDC 200 and etofenprox (MTI500) in which the central region is represented by a non-ester link, have been tested against one susceptible and two resistant strains (kdr and super-kdr) of houseflies (Musca domestica L.). A range of structural variations in the central region have been examined. Resistance factors mostly fell within narrow ranges for both resistant strains i.e. 10-50-fold resistance against kdr and 50-150-fold against super-kdr ; thus no correlation of resistance with structural features was detectable for this region. Other changes examined were the substituent on the phenyl ring in the 'acid' component and the bridging group in the 'alcohol' component where small variations in response were observed. Examination of the effect of varying the 'alcohol' side chain was limited by lack of active analogues.

Synthesis of Non-Ester Pyrethroids Having a 1-Fluoro-1-methylethyl Group Using 1,2-Migration of an Aryl Group

Abstract When 1,4-diaryl-4-methyl-1,3-pentanediol was treated with diethylaminosulfur trifluoride to introduce fluorine atoms into the central link, 1,2-aryl group migration products which have a 1-fluoro-1-methylethyl group were obtained as two diastereomers. Utilizing this migration, some non-ester pyrethroids possessing a 1-fluoro-1-methylethyl group were prepared. The reactivity of other fluorinating reagents is also discussed.

Gas chromatographic and mass spectrometric studies on pyrethroid photo- and biotransformation

Applications of high resolution gas chromatography (GC) and mass spectrometry (MS) in pesticide chemistry are demonstrated by pyrethroid photo- and biotransformation studies. Degradation of chrysanthemate pyrethroids (e.g. the natural pyrethrins, allethrin, tetramethrin and cyphenothrin) used as indoor insecticides is investigated by GC-MS using negative chemical ionization (NCI). Ozonolysis results in the formation of carbox-aldehydes as major indoor transformation products. In vitro metabolism of (S)-bioallethrin and the natural pyrethrins by NADPH dependent oxidases is studied using GC-MS with positive chemical ionization (PCI). Interpretation of the PCI mass spectra yields molecular weight and structural information about the metabolites and their derivatives. The photochemistry of novel non-ester pyrethroids with ether or alkane central linkages such as ethofenprox is investigated by electron impact (EI) GC-MS.

ChemInform Abstract: Synthesis of Some Fluorinated Non‐Ester Pyrethroids

ChemInform Abstract: Synthesis of Some Fluorinated Non‐Ester Pyrethroids

Symptomatic and neurophysiological activities of new synthetic non-ester pyrethroids, ethofenprox, MTI-800, and related compounds

Ethofenprox (MTI-500), MTI-800, and related compounds, which have a m-phenoxybenzyl moiety but lack ester bonding, were compared with DDT-type compounds and pyrethroid insecticides for their lethal and convulsive activities toward American cockroaches. The most potent among them ranked between phenothrin and cyphenothrin. Neurophysiological effects were also examined by extra- and intracellular recording and voltage clamp techniques. Some derivatives induced repetitive discharges in the excised central nerve cord of the American cockroach. The after-potential recorded intracellularly from the crayfish giant axon was markedly increased by some compounds. Voltage clamp experiments with the crayfish giant axon showed that ethofenprox decreased the peak sodium current and induced a large residual current during a step depolarization. It also induced a large and prolonged tail current after a step repolarization of the membrane. The effects of the test compounds on the action potential and the sodium current were similar to those of DDT-type compounds and the pyrethroids such as allethrin and phenothrin. A shift of sodium channel population from normal to modified was thought to result in modifications of the sodium current which, in turn, cause the increase in after-potential and the induction of repetitive discharges.