Temefos targets acetylcholinesterase (AChE), an enzyme essential for neurotransmission in insects. By inhibiting AChE, temefos prevents the breakdown of acetylcholine at synaptic junctions, leading to the accumulation of acetylcholine and continuous nerve stimulation. This results in paralysis and death of the target organism. The compound is a non-systemic insecticide with contact and stomach action.

In vitro, temefos inhibits acetylcholinesterase activity in target organisms. Its activity is assessed by measuring the inhibition of AChE in enzyme preparations from insects or by using purified enzyme. IC50 values are calculated from dose-response curves. The compound's selectivity for insect AChE over mammalian AChE contributes to its safety profile.

In vivo, temefos is used as a larvicide for the control of mosquito larvae in water bodies, including drinking water storage containers. It is also used for the control of black fly and other aquatic insect pests. The compound is applied as a liquid formulation or as granules. Its persistence in water depends on environmental conditions.

In vitro enzyme assays for temefos measure its inhibition of acetylcholinesterase (AChE) activity. The enzyme is incubated with its substrate (acetylthiocholine) and varying concentrations of the compound. The rate of substrate hydrolysis is measured spectrophotometrically using Ellman's reagent. IC50 values are calculated from dose-response curves. The compound's mechanism as an irreversible AChE inhibitor is confirmed by the time-dependent nature of inhibition.

In vitro cell-based assays for temefos use insect cell lines or neuronal preparations to assess its effects on cholinergic signaling. Cells are treated with serial dilutions of the compound, and AChE activity is measured. The compound's effects on cell viability and neuronal function are assessed in parallel.

In vivo animal models for temefos include mosquito larvae and other aquatic insects for efficacy testing. The compound is added to water containing larvae, and mortality is assessed over time. Dose-response studies establish the effective concentration for larval control (LC50). Environmental fate studies assess the compound's persistence and degradation in water and sediment.

Absorption, Distribution and Excretion
Skin permeability of 14C-labeled termethin was determined in mice, rabbits, and dogs. Absorption was assessed by monitoring radioactivity excreted in urine and feces over 7 days and analyzing tissue samples. The expected absorption was less than 3% of the administered dose. No evidence of radioactive material retention or accumulation in the body was found. In guinea pigs, oral absorption was significantly lower than in mice, and bile excretion of metabolites was confirmed. When mice were orally administered 3H-labeled termethin, blood radioactivity peaked between 5 and 8 hours and then dissipated within a half-life of approximately 10 hours. Significant radioactivity was found only in the gastrointestinal tract and fat. In feces and fat, most of the radioactivity originated from unmetabolized pesticides, but trace amounts of sulfoxides were also present. Trace amounts of termethin were found in urine… In mammals, termethin is primarily excreted in unmetabolized form via feces and urine.
Metabolisms/Metabolites
Studies using tritium-labeled abatazone showed that this insecticide is relatively resistant to metabolic degradation. Residue on bean leaves… consisted primarily of intact abatazone, representing approximately 70% of the applied dose. The main metabolite was a sulfoxide derivative, accounting for less than 5% of the dose. Trace amounts of sulfone derivatives, oxygen analogs, and glycosidic conjugates of the phenolic hydrolysates of abatazone and its sulfoxide and sulfone derivatives were also observed.
When rats were fed abatazone, 60% of the substance appeared in feces as oxygen analogs of abatazone and its sulfoxide. Thiodiols, sulfinyldiols, and sulfonyldiols were also detected. In urine, sulfate and glucosinolate conjugates of the hydrolysates of abatazone and its sulfoxide, as well as sulfone analogs, accounted for 39.5% of the total administered dose. …Five compounds found in feces and three compounds found in urine were not identified.
Aedes aegypti L. larvae metabolize abat to abat sulfoxides and sulfones, oxygen analogs and demethyl analogs. Some conjugates are also generated. In vitro, all expected metabolites are present in vivo as intact esters or hydrolysates...
Abbat production, abat sulfoxides and thiodiols in rats. /Excerpt from Table/
For more complete metabolite/metabolite data for TEMEPHOS (8 in total), please visit the HSDB record page.

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Biological half-life
When (3)H temetphos was administered orally to rats, the radioactivity in the blood peaked between 5 and 8 hours and then dissipated with a half-life of about 10 hours.
Temefos has a molecular formula of C16H20O6P2S3 and a molecular weight of 466.47. The compound is a phosphorothioate insecticide that is insoluble in water and soluble in organic solvents. It is stored at room temperature. The compound is used as a larvicide in public health and agricultural applications. Its persistence in the environment is influenced by pH, temperature, and microbial activity.

Interactions
The mixture of abat and malathion was significantly more toxic to rats than either compound alone. Non-human Toxicity Values Dermal LD50 for female rabbits: 970 mg/kg; Dermal LD50 for male rabbits: 1930 mg/kg; Oral LD50 for male rats: 8600 mg/kg; Oral LD50 for female rats: 13,000 mg/kg. For more complete non-human toxicity data for TEMEPHOS (15 compounds), please visit the HSDB record page.
The toxicity profile of temefos is characterized by low acute toxicity to mammals, birds, and fish at recommended application rates. The compound is more toxic to aquatic invertebrates. Occupational exposure may cause skin and eye irritation. The compound is not considered genotoxic or carcinogenic at relevant exposure levels. Appropriate safety precautions should be taken during handling and application.

Terfenoxam appears as a white crystalline solid or liquid (above 87 °F). It is used as an insecticide. Industrial grade is a viscous brown liquid. (NIOSH, 2024)
Terfenoxam is an organosulfur compound, a diphenyl sulfide, in which the hydrogen at the para-position of each phenyl group is replaced by an oxygen group (dimethoxyphosphothiophosphate). It can be used as an EC 3.1.1.7 (acetylcholinesterase) inhibitor, acaricide, agricultural chemical, and ectoparasite killer. It is an organothiophosphate, organothiophosphate insecticide, and organosulfur compound. It is functionally related to 4,4'-thiodiphenol.
Diphosphothiophosphate has been used in studies investigating the treatment of malaria with Plasmodium falciparum.
An organothiophosphate insecticide.
Mechanism of Action

Abet is a cholinesterase inhibitor insecticide. Organophosphate insecticides primarily poison insects and humans by phosphorylating acetylcholinesterase in nerve endings. /Organophosphate cholinesterase inhibitor insecticides/
Temefos is an organophosphate insecticide used primarily for the control of mosquito larvae and other aquatic insect pests. It is also known as temephos. The compound is a phosphorothioate that inhibits acetylcholinesterase, leading to paralysis and death of target organisms. Temefos is widely used in public health programs for vector control and in agricultural settings. It is used for research and pest control purposes.

C16H20O6P2S3

466.46

465.989

3383-96-8

Temephos-d12;1219795-39-7

5392

Colorless crystals
White, crystalline solid or liquid (above 87 degrees F) [Note: Technical grade is a brown, viscous liquid].

1.4±0.1 g/cm3

518.5±60.0 °C at 760 mmHg

30-31°C

267.4±32.9 °C

0.0±1.3 mmHg at 25°C

1.613

5.96

0

9

10

27

474

0

COP(OC(C=C1)=CC=C1SC2=CC=C(OP(OC)(OC)=S)C=C2)(OC)=S

WWJZWCUNLNYYAU-UHFFFAOYSA-N

InChI=1S/C16H20O6P2S3/c1-17-23(25,18-2)21-13-5-9-15(10-6-13)27-16-11-7-14(8-12-16)22-24(26,19-3)20-4/h5-12H,1-4H3

[4-(4-dimethoxyphosphinothioyloxyphenyl)sulfanylphenoxy]-dimethoxy-sulfanylidene-λ5-phosphane

Bithion; Abate; Temefos

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~100 mg/mL (~214.38 mM)

Solubility in Formulation 1: 2.5 mg/mL (5.36 mM) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), suspension solution; with sonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (5.36 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)