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PubMed2001

New insecticidal rocaglamide derivatives and related compounds from Aglaia oligophylla.

Organic-soluble extracts of the twigs of Aglaia oligophylla collected in Vietnam yielded four insecticidal cyclopentatetrahydrobenzofurans of the rocaglamide type including one new natural product (compound 4). Moreover, two cyclopentatetrahydrobenzopyran derivatives, belonging to the aglain and aglaforbesin types, respectively, were also isolated. The aglaforbesin derivative 6 proved likewise to be a new natural product. All isolated rocaglamide, aglain, and aglaforbesin derivatives have a characteristic methylenedioxy substituent linked to C-6 and C-7 or to C-7 and C-8, respectively. Structure elucidation of the new natural products and the determination of the absolute configuration of compound 1 by calculation of its CD spectrum with molecular dynamics simulation are described. All isolated rocaglamide derivatives exhibited strong insecticidal activity toward neonate larvae of the polyphageous pest insect Spodoptera littoralis when incorporated into an artificial diet, with LC(50) values varying between 2.15 and 6.52 ppm.

Animals↗
PubMed2006

Photoactivated insecticidal thiophene derivatives from Xanthopappus subacaulis.

Three new photoactivated insecticidal thiophene derivatives, xanthopappins A-C (1-3), were isolated from Xanthopappus subacaulis, along with three known thiophene acetylenes, 5-hydroxymethyl-2-(E)-hept-5-ene-1,3-diynylthiophene (4), 5-(1,2-dihydroxyethyl)-2-(E)-hept-5-ene-1,3-diynylthiophene (5), and 5-(1,2-diacetoxyethyl)-2-(E)-hept-5-ene-1,3-diynylthiophene (6). The structures of 1-3 were elucidated by spectroscopic methods. Compounds 1-6 exhibited significant photoactivated insecticidal activity against the fourth-instar larvae of the Asian tiger mosquito.

Aedes↗
PubMed2006

Discovery, synthesis, and insecticidal activity of cycloaspeptide E.

Several Penicillia and one Tricothecium strain produced a new, insecticidally active member of the cycloaspeptide family, with the proposed name cycloaspeptide E (1). The structure, which was determined on the basis of spectroscopic (NMR, UV, MS) data and Marfey amino acid analysis, was the tyrosine desoxy version of cycloaspeptide A (2). Two synthetic routes to compound 1 were developed: one a partial synthesis from 2 and the other a total synthesis from methyl alaninate hydrochloride. Cycloaspeptide E, the first member of this series not to contain a tyrosine moiety, is also the first to be reported with insecticidal activity.

Animals↗
PubMedDate not supplied

Ryanodyl 3-(pyridine-3-carboxylate): a novel ryanoid from Ryania insecticide.

Ryanodyl 3-(pyridine-3-carboxylate) was isolated as a minor component from the wet CHCl3 extract of Ryania insecticide, and its structure was assigned by chemical and spectroscopic methods. This compound is essentially inactive compared with ryanodine for insecticidal activity against Musca domestica adults and Tribolium castaneum larvae, for toxicity to mice, and for competition with [3H]ryanodine at the Ca(2+)-ryanodine receptor complex of skeletal muscle.

Animals↗
PubMed1997

Methyl 4-hydroxy-3-(3'-methyl-2'-butenyl)benzoate, major insecticidal principle from Piper guanacastensis.

The CHCl3-soluble extract of Piper guanacastensis (Piperaceae) was found to have noteworthy insecticidal activity to Aedes atropalpus mosquito larvae (LC50 80.5 micrograms/mL). Bioassay-guided fractionation afforded methyl 4-hydroxy-3-(3'-methyl-2'-butenyl)benzoate (1) as the major bioactive constituent (LC50 20.5 micrograms/mL). The separation of compound 1 from its transesterification artifact (2), ethyl 4-hydroxy-3-(3'-methyl-2'-butenyl)benzoate, was achieved by recycling reversed-phase HPLC. The flavonoids acacetin, chrysin, and pinostrobin were also isolated from the active fraction but did not display insecticidal properties.

Aedes↗
PubMed2005

Neonicotinoid nitroguanidine insecticide metabolites: synthesis and nicotinic receptor potency of guanidines, aminoguanidines, and their derivatives.

Four neonicotinoid nitroguanidine insecticides (imidacloprid, thiamethoxam, clothianidin, and dinotefuran) acting as nicotinic agonists account for 10-15% of worldwide insecticide sales. General methods are needed for synthesis of their guanidine and aminoguanidine metabolites so they may be used as analytical standards and for evaluation of nicotinic receptor potency. The guanidines are obtained by treating the parent nitroguanidines with Fe powder in aqueous C2H5OH containing NH4Cl and isolated by silica chromatography. The aminoguanidines are prepared as mixtures with the guanidines on reaction of the parent nitroguanidines and Zn powder in glacial acetic acid. The imidacloprid aminoguanidine is isolated as the acetone imine or trifluoroacetamide and the clothianidin and dinotefuran aminoguanidines as the acetone imines using silica chromatography. Deprotection under acidic conditions then leads to the aminoguanidine.HCl salts. Because of stability considerations, a pH partitioning method is used to separate thiamethoxam aminoguanidine and guanidine. An alternate procedure to the aminoguanidine of imidacloprid (but not thiamethoxam, clothianidin, or dinotefuran) is reaction with hydrazine hydrate and NH4Cl in anhydrous C2H5OH. Ambiguities in further biological reactions are clarified by synthesizing authentic standards of three purported metabolites formed via the imidacloprid aminoguanidine: the 1,2,4-triazol-3-one derivative with ethyl chloroformate or ethyl pyrocarbonate, the acetaldehyde imine with acetaldehyde, and the 3-methyl-1,2,4-triazin-4-one derivative with ethyl pyruvate in refluxing toluene. The purported triazolone metabolite is reassigned as the aminoguanidine acetaldehyde imine probably formed as an artifact from acetaldehyde present in the ethyl acetate used for metabolite extraction. Potency at the Drosophila nicotinic receptor is greatly decreased on converting a nitroguanidine to a guanidine or aminoguanidine. In sharp contrast, potency at the vertebrate alpha4beta2 nicotinic receptor is generally increased on conversion from the nitroguanidine to aminoguanidine and particularly guanidine derivatives.

Amination↗
PubMed1997

Acephate insecticide toxicity: safety conferred by inhibition of the bioactivating carboxyamidase by the metabolite methamidophos.

Acephate is an important systemic organophosphorus insecticide with toxicity attributed to bioactivation on metabolic conversion to methamidophos (or an oxidized metabolite thereof) which acts as an acetylcholinesterase (AChE) inhibitor. The selective toxicity of acephate is considered to be due to facile conversion to methamidophos in insects but not mammals. We show in the present investigation that a carboxyamidase activates acephate in mice and in turn undergoes inhibition by the hydrolysis product, i.e., methamidophos; thus, the bioactivation is started but immediately turned off. These relationships are established by finding that 4 h pretreatment of mice with methamidophos i.p. at 5 mg/kg has the following effects on acephate action: reduces methamidophos and acephate levels in liver by 30-60% in the first 2 h after i.p. acephate dosage; inhibits the liver carboxyamidase cleaving [14CH3S]acephate to [14CH3S]methamidiphos with 50% block at approximately 1 mg/kg; strongly inhibits 14CO2 liberation from [CH3(14)C(O)]acephate in vivo; markedly alters the pattern of urinary metabolites of acephate by increasing O- and S-demethylation products retaining the carboxyamide moiety; greatly reduces the brain AChE inhibition following acephate treatment; doubles the LD50 of i.p.-administered acephate from 540 to 1140 mg/kg. Methamidophos pretreatment in rats also markedly alters the metabolism of dimethoate (another systemic insecticide) from principally carboxyamide hydrolysis to mainly other pathways. In contrast, methamidophos pretreatment of houseflies does not alter the acephate-induced toxicity and brain AChE inhibition. The safety of acephate in mammals therefore appears to be due to conversion in small part to methamidophos which, acting directly or as a metabolite, is a potent carboxyamidase inhibitor, thereby blocking further activation.

Amidohydrolases↗
PubMed2001

The use of a Daphnia magna bioassay for rapid screening of acute intoxications with insecticides in dogs and cats.

Sudden death due to acute insecticide intoxications occurs frequently in dogs and cats. The absence of characteristic lesions at autopsy often renders post-mortem diagnosis dependent on the analysis of samples taken from the carcase at autopsy. In the present study, a bioassay utilizing Daphnia magna was proposed and tested as a rapid screening method for acute intoxications in dogs and cats. The bioassay was shown to be highly sensitive for detecting carbamate and organophosphate insecticides in the stomach contents. Generally. the mean survival time of the waterfleas in the control group was 5.17 h (SD = 1.24) and in the intoxicated group 1.32 h (SD = 1.49). during a 6 h observation period. If a cut-off is set at 4 h, this Daphnia bioassay gave 5.5% false negative results and 18.2% false positive results. using the results of toxicological analyses as a gold standard.

Animals↗
PubMed2002

Effects of a mixture of two insecticides in freshwater microcosms: II. Responses of plankton and ecological risk assessment.

This paper reports on the chronic effects of a mixture of the insecticides chlorpyrifos and lindane in freshwater microcosms. Chronic treatment levels corresponding to concentrations of 0, 0.005, 0.01, 0.05, 0.1 and 0.5 times the LC50 of the most sensitive standard test organism were evaluated. The zooplankton community structure was altered from the 0.05 * LC50 treatment level upwards. Cladocerans were the most susceptible group, followed by Copepoda and Ostracoda. Rotifera increased in abundance at the higher treatment levels. Increased abundance of some phytoplankton taxa and increased chlorophyll-a levels were found at the two highest treatment levels, most probably a consequence of decreased grazing pressure. Threshold levels for the mixture, both at population and community/ecosystem level, corresponded well with those reported in the literature for the individual compounds. The overall risk assessment indicates no antagonistic or synergistic effects of the mixture at ecosystem level. It was found that the safety factors set by the Uniform Principles for individual compounds also ensure protection against chronic exposure to a mixture of insecticides at community level, though not always at species level.

Animals↗
PubMed2002

Organochlorine insecticide residues in drinking and ground water in and around Delhi.

A multiresidue method was developed for the estimation of 15 organochlorine pesticides in water. 50 samples of drinking water supplied by the Municipal Corporation to the residential areas of Delhi and 20 ground water samples from nearby villages used for irrigation were monitored for the presence of organochlorine insecticides by the method developed. Although, organochlorine pesticides were detected in the ground water and irrigation water samples, the levels of pesticides were below the Maximum Contaminant Level as prescribed by WHO. No organochlorine insecticides were detected in any of the drinking water samples.

Cities↗
PubMed2002

In vitro cytotoxicity of the organophosphorus insecticide methylparathion to FG-9307, the gill cell line of flounder (Paralichthys olivaceus).

FG-9307, a cell line derived from the gill of flounder Paralichthys olivaceus, was used to determine the acute cytotoxic effects of the organophosphorus insecticide methylparathion. The cytotoxic effects of methylparathion were initially measured by three endpoint systems: neutral red (NR) uptake assay, tetrazolium (MTT) assay, and cell protein assay. Results indicated that concentrations of methylparathion ranging from 5 microg/ml to 60 microg/ml were toxic, and there was no significant difference in cytotoxic effects between the three test systems. Thus, the FG-9307 cell line is one of several choices for evaluating the acute toxicities of organophosphorus insecticides such as methylparathion. The ultrastructure of the cells was also studied. It was found that the ultrastructure of the cells was markedly altered by methylparathion, as evidenced by dilation of mitochondria, breakdown of rough endoplasmic reticulum, nuclear necrosis, and production of numerous lysosomes and lipid vacuoles. This appears to be the first report that a marine fish cell line can be used for acute in vitro cytotoxicity evaluation of methylparathion.

Animals↗
PubMed2003

Chemical stimulants of leaf-trenching by cabbage loopers: natural products, neurotransmitters, insecticides, and drugs.

Larvae of the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae), often transect leaves with a narrow trench before eating the distal section. The trench reduces larval exposure to exudates, such as latex, during feeding. Plant species that do not emit exudate, such as Plantago lanceolata, are not trenched. However, if exudate is applied to a looper's mouth during feeding on P. lanceolata, the larva will often stop and cut a trench. Dissolved chemicals can be similarly applied and tested for effectiveness at triggering trenching. With this assay, I have documented that lactucin from lettuce latex (Lactuca sativa), myristicin from parsley oil (Petroselinum crispum), and lobeline from cardinal flower (Lobelia cardinalis) elicit trenching. These compounds are the first trenching stimulants reported. Several other constituents of lettuce and parsley, including some phenylpropanoids, monoterpenes, and furanocoumarins had little or no activity. Cucurbitacin E glycoside found in cucurbits, another plant family trenched by cabbage loopers, also was inactive. Lactucin, myristicin, and lobeline all affect the nervous system of mammals, with lobeline acting specifically as an antagonist of nicotinic acetylcholine receptors. To determine if cabbage loopers respond selectively to compounds active at acetylcholine synapses, I tested several neurotransmitters, insecticides, and drugs with known neurological activity, many of which triggered trenching. Active compounds included dopamine, serotonin, the insecticide imidacloprid, and various drugs such as ipratropium, apomorphine, buspirone, and metoclopramide. These results document that noxious plant chemicals trigger trenching, that loopers respond to different trenching stimulants in different plants, that diverse neuroactive chemicals elicit the behavior, and that feeding deterrents are not all trenching stimulants. The trenching assay offers a novel approach for identifying defensive plant compounds with potential uses in agriculture or medicine. Cabbage loopers in the lab and field routinely trench and feed on plants in the Asteraceae and Apiaceae. However, first and third instar larvae enclosed on Lobelia cardinalis (Campanulaceae) failed to develop, even though the third instar larvae attempted to trench. Trenching ability does not guarantee effective feeding on plants with canal-borne exudates. Cabbage loopers must not only recognize and respond to trenching stimulants, they must also tolerate exudates during the trenching procedure to disable canalicular defenses.

Animals↗
PubMed2003

Fatal lipoid pneumonia due to bronco-aspiration of isoparaffin after ingestion of an organophosphate insecticide.

A 66-year-old-male patient with a history of depression voluntarily ingested around 400 ml of an insecticide composed of 5% methylparathion, 75% isoparaffin, 8% etoxylated oleic acid, 4% 1,2,4-trimethylbenzene, 6% naphtha, 1% 1,3,5- trimethylbenzene, 0.4% propylbenzene and 0.3% xylene. The patient was conscious and alert at admission. Gastric lavage was performed and activated charcoal administered. There were no clinical symptoms of organophospate ingestion despite reduced concentrations of erythrocyte and plasma cholinesterase. Chest X-ray showed pulmonary infiltrate compatible with bronco-aspiration. The patient evolved to respiratory failure refractory to treatment and died from multiorganic failure 23 days after ingesting the insecticide. The pathological findings included a pulmonary fibrosis in the alveolar spaces which caused enlargement of the intra-alveolar septa. Abundant lipin-laden macrophages were observed within the alveolar spaces. We review the most relevant aspects of cases of fatal lipoid pneumonia and point out that on occasion severe or fatal intoxication is due to the substances accompanying the active ingredients.

Aged↗
PubMed1993

A point mutation in a Drosophila GABA receptor confers insecticide resistance.

Vertebrates and invertebrates both have GABA (gamma-aminobutyric acid) as a major inhibitory neurotransmitter. GABAA receptors in vertebrates assemble as heteromultimers to form an integral chloride ion channel. These receptors are targets for drugs and pesticides and are also implicated in seizure-related diseases. Picrotoxinin (PTX) and cyclodiene insecticides are GABAA receptor antagonists which competitively displace each other from the same binding site. Insects and vertebrates showing resistance to cyclodienes also show cross-resistance to PTX. Previously, we used a field-isolated Drosophila mutant Rdl (Resistant to dieldrin) insensitive to PTX and cyclodienes to clone a putative GABA receptor. Here we report the functional expression and novel pharmacology of this GABA receptor and examine the functionality of a resistance-associated point mutation (alanine to serine) within the second membrane-spanning domain, the region thought to line the chloride ion channel pore. This substitution is found globally in Drosophila populations. This mutation not only identifies a single amino acid conferring high levels of resistance to the important GABA receptor antagonist PTX but also, by conferring resistance to cyclodienes, may account for over 60% of reported cases of insecticide resistance.

Alanine↗
PubMed1992

Expansion of insecticidal host range of Bacillus thuringiensis by in vivo genetic recombination.

We describe a novel approach for the insertion of an insecticidal toxin gene into a resident plasmid in Bacillus thuringiensis (Bt). A gene encoding a coleopteran-specific toxin was cloned within a fragment of IS232 and inserted into a plasmid thermosensitive for replication in Bt. The plasmid was used to transform a Bt strain toxic to lepidoptera, and the transformants were then selected at non-permissive temperature for clones in which the vector had integrated into a copy of IS232 present on a resident plasmid. A second recombination event was selected such that the vector was eliminated and the newly introduced toxin gene was conserved. The resulting strain contained only DNA of Bt origin, and displayed insecticidal activity against both lepidoptera and coleoptera.

Bacillus thuringiensis↗
PubMed2001

Indoxacarb, an oxadiazine insecticide, blocks insect neuronal sodium channels.

1. Decarbomethoxyllated JW062 (DCJW), the active component of a new oxadiazine insecticide DPX-JW062 (Indoxacarb), was tested on action potentials and the inward sodium current recorded from short-term cultured dorsal unpaired median neurones of the cockroach Periplaneta americana. 2. Under whole-cell current-clamp conditions, 100 nM DCJW reduced the amplitude of action potentials and induced a large hyperpolarization of the resting membrane potential associated with a 41% increase in input resistance. 3. In voltage-clamp, DCJW resulted in a dose-dependent inhibition (IC(50) 28 nM) of the peak sodium current. Based on IC(50) values, the effect of DCJW was about 10 fold less potent than tetrodotoxin (TTX) but 1000 fold more potent than the local anaesthetic lidocaine. DCJW (100 nM) was without effect on activation properties of the sodium current, reversal potential, voltage dependence of sodium conductance and on both fast and slow steady-state inactivations. 4. TTX (2 nM) resulted in 48% inhibition of the peak inward sodium current. Co-application of TTX (2 nM) with various concentrations of DCJW produced an additional inhibition of the peak inward current, indicating that the blocking actions of DCJW and TTX were distinct. Co-application of lidocaine (IC(50) 30 microM) with various concentrations of DCJW produced a reduction of the apparent potency of DCJW, suggesting that DCJW and lidocaine acted at the same site. 5. DCJW (100 nM) did not affect inward calcium or outward potassium currents. 6. This study describes, for the first time, the action on insect neuronal voltage-dependent sodium channels of Indoxacarb, a new class of insecticides.

Action Potentials↗
PubMedDate not supplied

House dust levels of selected insecticides and a herbicide measured by the EL and LWW samplers and comparisons to hand rinses and urine metabolites.

During the Minnesota Children's Pesticide Exposure Study (MNCPES), comparisons were made between the insecticide/herbicide loadings obtained with two household dust/insecticide or herbicide samplers: the Edwards and Lioy (EL) press sampler (used for dust collection from carpets or other surfaces) and the Lioy, Waimnan and Weisel (LWW) surface wipe sampler. The results were compared with hand rinse levels, and urine metabolite levels obtained from 102 children (ages 3-13). All measurements were made during a 1-week sampling period, and information was obtained on household pesticide use and each child's activities. Of the homes, <5% had recent spot uses of a pesticide but none had recent general applications. The analyses focused primarily on atrazine (a herbicide), and malathion, diazinon, and chlorpyrifos (insecticides). Metabolites were measured for atrazine, malathion and chlorpyrifos. The atrazine levels obtained using the EL indicate that this compound was transported into the home by an unquantified transport mechanism (e.g. tracking of soil). Two malathion hand rinse values exceeded >170 ng/cm2, suggesting that since indoor surface levels were low, these children had other sources of exposure. Atrazine, chlorpyrifos and malathion were detectable in >30% of the homes by the EL, LWW or hand rinse. Only chlorpyrifos had detectable levels in > or = 50% of the samples for all types, i.e. compound or metabolite, which is consistent with it being a common household pesticide. The median (and maximum) chlorpyrifos levels for the EL surface, EL carpet, LWW surface (two rooms), hand rinse, and urine metabolites were: 0.07 (32.6) ng/cm2; 0.07 (44.5) ng/cm2; 0.34 (3.64) ng/cm2; 0.42 (14.4) ng/cm2; 0.03 (2.14) ng/hand and 6.9 (59.0) microg/g, respectively. A strong correlation was found for chlorpyrifos between the EL surface and carpet samples. Chlorpyrifos levels detected by LWW had a different distribution and concentration range than the EL, indicating that it collected more than the surface dislodgeable insecticide. EL was directly comparable to the hand rinse or urine levels, but only the LWW had a weak correlation with hand rinse levels, suggesting that the children had other sources of chlorpyrifos exposure. Thus, mechanistic exposure studies are needed to more accurately establish exposure dose relationships in residential settings.

Adolescent↗
PubMed1991

Determination of the insecticide promecarb by fluorogenic labelling with dansyl chloride.

The use of spectrofluorimetry to determine the fluorescent derivative of the insecticide promecarb, following hydrolysis to the corresponding phenol in basic media and subsequent coupling with the labelling agent dansyl chloride, is described and discussed. A study of media of different basicity and of different temperatures for both reactions gave optimum conditions of 20 min for the hydrolysis reaction and 10 min for the labelling reaction at 55 degrees C in 0.05 mol dm-3 sodium hydrogen carbonate solution with a reagent to insecticide ratio of 12:1. The effect of the solvent on the formation of the dansyl derivative and on the extraction process was studied using nine and seven solvents, respectively. The use of a mixture of acetone and water (50 + 50, v/v) and an extraction into cyclohexane gave the best results. The minimum detectable concentration of promecarb in the experimental assays was 100 ng ml-1. The error and relative standard deviation at a concentration level of 0.6 micrograms ml-1 were 9.7 and 10.9%, respectively. Air samples containing promecarb at different concentration levels were analysed.

Air Pollution, Indoor↗