Chemistry:Diafenthiuron

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Short description: Organosulfur insecticide
Diafenthiuron
Diafenthiuron.svg
Names
IUPAC name
1-tert-Butyl-3-[4-phenoxy-2,6-di(propan-2-yl)phenyl]thiourea
Other names
1-tert-Butyl-3-(2,6-diisopropyl-4-phenoxyphenyl)thiourea
Identifiers
3D model (JSmol)
8343025
ChEBI
ChemSpider
EC Number
  • 616-885-7
KEGG
RTECS number
  • XN9100000
UNII
Properties
C23H32N2OS
Molar mass 384.58 g·mol−1
Hazards
GHS pictograms GHS06: ToxicGHS07: HarmfulGHS08: Health hazardGHS09: Environmental hazard
GHS Signal word Danger
H331, H332, H373, H410
P260, P261, P271, P273, P304+340, P316Script error: No such module "Preview warning".Category:GHS errors, P317Script error: No such module "Preview warning".Category:GHS errors, P319Script error: No such module "Preview warning".Category:GHS errors, P321, P391, P403+233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Tracking categories (test):

Diafenthioron is a pesticide, specifically an insecticide. It is a chemical compound which belongs to the thiourea group. Diafenthiuron is sold under the brand names Derby, Diron, Pegasus, Polar and Polo.

History

Diafenthiuron was introduced to the market in 1990 by a pharmaceutical company called Ciba-Geigy in Switzerland and due to rising environmental concerns it is no longer approved in Switzerland and other countries of the European Union.[2] However, until 2001, Switzerland still produced and exported the compound to other countries where its use as an agricultural pesticide was still legal.[3][4]

Structure and reactivity

Diafenthiuron is an phenol ether of molecular weight 384.6 g/mole and containing two 6-carbon rings attached to an oxygen and nitrilo (tert-butylcarbamate) group substituting for a hydrogen atom at position 2. It is highly soluble in multiple organic solvents however dissolves poorly in aqueous solutions due to the hydrocarbon rich regions and oxygen atom which do not form H bonds with water molecules.[5] Therefore diafenthiuron contamination of underground water storages by leaching is unlikely. Its lack of water solubility (partition coefficient logPow = 5.76) and strong sorption capacity, means it has the ability to accumulate persistently in aquatic and soil systems.[2]

It is a broad spectrum, both systemic and contact as well as stomach activity synthetic pesticide impairing mitochondrial function in target pests (phytophagous mites).[6][7] Due to progressive break-down of diafenthiuron to non-toxic metabolites, it poses no significant reactivity threat in the field of ecotoxicology (Hazard class III = slightly hazardous). However, its highly reactive metabolite carbodiimide (a result of S-oxidation → either non-enzymatic (light-catalyzed), P450 monooxygenases, or by FAD monooxygenases) binds to the mitochondrial ATPase and porin, inhibiting ATP production.[8]

Synthesis

The synthesis of diafenthiuron starts with phenol reacting with 2,6-diisopropyl-4-chloroaniline, creating the intermediate product 2,6-diisopropyl-4-phenoxyaniline. 2,6-diisopropyl-4-phenoxyaniline will then undergo a reaction with thiophosgene and form N-(2,6-diisopropyl-4-phenoxyphenyl)isothiocyanate. This in turn will react with tert-butylamine and form diafenthurion.[9]

Synthesis of Diafenthiuron

Mechanism of action

Diafenthiuron is photochemically or metabolically transformed into a highly reactive metabolite, Diafenthiuron carbodiimide, which covalently and irreversibly binds to microsomal glucose-6-phosphate translocase, a part of the adenosine triphosphatase (ATPase) complex. The binding inhibits the function of the ATPase complex due to the modification of a single sulfhydryl/amino phosphate group of the glucose-6-phosphate translocase. Therefore, substrates such as inorganic phosphate, carbamoyl phosphate and pyrophosphate cross the microsomal membrane freely without the catalytic function of the translocase; ATP production is inhibited. [6] Diafenthiuron carbodiimide also affects mitochondrial porins, but due to the fact that the function of these mitochondrial porins is not fully known yet, the effects of the carbodiimide on these porins is also not understood. In summary, diafenthiuron inhibits the process of mitochondrial respiration by binding to various mitochondrial components.

Efficacy and side effects

Efficacy

Diafenthiuron has shown high efficacy against many important agricultural pests, including mites, aphids, thrips, and whiteflies. Several studies have demonstrated the efficacy of diafenthiuron in controlling various pests affecting a variety of crops. For example, diafenthiuron has shown to be effective against cotton bollworm, cotton jassid, and spider mites.[10] With citrus fruits, it has been shown to control citrus rust mites and aphids.[11][12] With grapes, diafenthiuron has shown to be effective against grape leafhoppers and mites.[13] The efficacy of diafenthiuron is dependent on several factors; the target pest species, the stage of the pest's life cycle, and environmental conditions such as temperature and humidity. Next to that, the repeated use of diafenthiuron can lead to the development of resistance in target pests, reducing the efficacy of the insecticide over time.

Side effects

Apart from enzymatic conversion, diafenthiuron readily dissolves in organic solvents or is broken down by sunlight into two major by-products; diafenthiuron carbodiimide and diafenthiuron urea. In aqueous systems, the carbodiimide was further observed to be photo-transformed into diafenthiuron urea in the presence of sunlight; a key photolysis pathway in diafenthiuron breakdown in the environment.[14]

Due to aerial application of the pesticide, its entering into fresh water bodies has observable effects on non-target organisms. Sub lethal doses (0.0075 mg/L) in both short and long term application had significant adverse effects on serum, hematological and elemental concentrations of fish which suggests that the use of diafenthiuron as a pesticide threatens the stability of aquatic food webs.[15] The second metabolite, urea, puts an additional strain on aquatic systems.

Rapid photodegradation of diafenthiuron and its metabolites in water and soil suggests limited accumulation capacity, despite the bioaccumulation potential of ~800. However, a pond mesocosm study did not exhibit such effects in vivo, possibly due to the rapid time period needed for degradation of 50% of the product (DT50) being <22 hours.[16] This considerably decreases the time frame of possible exposure and therefore reduces inducible toxicity by diafenthiuron metabolism.

Toxicology assessments and evaluations of dietary intake residues suggest that there are no adverse effects on human health due to exposure to agricultural residues of diafenthiuron application.[16]

Toxicity data

Toxicity data[2]
Measurement Method of administration LD50
1 Acute toxicity data inhalation (rat) 558 mg/m3
2 Acute toxicity data oral (duck) >1500 mg/kg
3 Acute toxicity data oral (quail) >1500 mg/kg
4 Acute toxicity data oral (rat) 2068 mg/kg
5 Acute toxicity data skin (rat) >2 gm/kg
6 Other multiple dose data oral (dog) lowest published dose: 360 mg/kg/90D continuous

Effects on animals

When animals are exposed to diafenthiuron, both acute and chronic effects can occur. Different animal species can have different sensitivity to diafenthiuron depending on factors like size, metabolism, and exposure pathway. However, in general, aquatic organisms and bees suffer most from diafenthiuron exposure.

Aquatic life

Diafenthiuron can have adverse effects on aquatic life when it enters water bodies through runoff or spray drift. The effects depend on the concentration and duration of exposure, as well as the sensitivity of the aquatic species. Some potential effects of diafenthiuron include:

  1. Acute toxicity: diafenthiuron can be highly toxic, especially to invertebrates such as crustaceans and insects. Exposure to high concentrations of diafenthiuron can cause rapid death in these organisms.[17]
  2. Chronic toxicity: prolonged exposure to lower concentrations of diafenthiuron can lead to chronic effects. These effects can include reduced growth and reproduction, as well as changes in behavior and physiology.[18]

Bees

Bees can be exposed to diafenthiuron through the consumption of contaminated nectar and pollen. This can have adverse effects on health and survival. The effects of diafenthiuron on bees can include:

  1. Reduced foraging activity: exposure to diafenthiuron can cause behavioural changes in bees, reducing their foraging activity and impairing their ability to locate and collect food.[19]
  2. Reduced reproduction: exposure to diafenthiuron can reduce reproductive success, including the production of eggs and the survival chances of larvae.[20]
  3. Mortality: high levels of exposure to diafenthiuron can cause rapid mortality, especially in young or weak individuals.[19]

References

  1. ↑ "Diafenthiuron" (in en). https://pubchem.ncbi.nlm.nih.gov/compound/3034380#section=Safety-and-Hazards. 
  2. ↑ 2.0 2.1 2.2 PubChem. "Diafenthiuron" (in en). https://pubchem.ncbi.nlm.nih.gov/compound/3034380. 
  3. ↑ "Public Eye et al. vs. Syngenta" (in en-GB). https://www.oecdwatch.org/complaint/public-eye-et-al-vs-syngenta/. 
  4. ↑ "Strengere Bestimmungen für die Ausfuhr von Pflanzenschutzmitteln". https://www.admin.ch/gov/de/start/dokumentation/medienmitteilungen/bundesrat.msg-id-80711.html. 
  5. ↑ "Physical Properties of Ether" (in en). 2015-08-07. https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Ethers/Properties_of_Ethers/Physical_Properties_of_Ether. 
  6. ↑ 6.0 6.1 Ruder, F. J.; Kayser, H. (1993-06-01). "The Carbodiimide Product of Diafenthiuron Inhibits Mitochondria in Vivo" (in en). Pesticide Biochemistry and Physiology 46 (2): 96–106. doi:10.1006/pest.1993.1041. ISSN 0048-3575. https://www.sciencedirect.com/science/article/pii/S0048357583710412. 
  7. ↑ "HPM Chemicals & Fertilizers Ltd.". https://hpmindia.com/product-insecticidesdd.php#:~:text=Diafenthiuron%2047.8%25%20SC,%20a%20broad,of%20insecticide%20mode%20of%20action. 
  8. ↑ "Diafenthiuron". http://www.agropages.com/AgroData/Detail-416.htm. 
  9. ↑ Unger, Thomas A. (1996-12-31) (in en). Pesticide Synthesis Handbook. William Andrew. ISBN 978-0-8155-1853-2. https://books.google.com/books?id=-9cHDi8OOO4C. 
  10. ↑ Bajya, D. R.; Ranjith, M.; Lakharan, M. C.; Raza, S. (2016). "Efficacy of Diafenthiuron 47.8 SC Against Sucking Pests of Cotton and ITS Safety to Natural Enemies" (in en). Indian Journal of Entomology 78: 15. doi:10.5958/0974-8172.2016.00003.1. 
  11. ↑ Bagwani, Krishi (2015). "Journal of Eco-friendly Agriculture". Journal of Eco-friendly Agriculture 10 (2): 172–174. http://ecoagrijournal.com/wp-content/uploads/2019/10/Full-Paper-102.pdf. 
  12. ↑ Dalvaniya, D.; Patel, P.; Pareek, A.; Panickar, B. (2015). "Efficacy of some insecticides against citrus psylla, Diaphorina citri Kuwayama on kagzi lime" (in en). Journal of Entomological Research 39 (2): 141. doi:10.5958/0974-4576.2015.00009.2. 
  13. ↑ Assessment, US EPA National Center for Environmental (2009-03-15). "Bioefficacy of diafenthiuron 50 SC (Polo 50 SC) against grapevine pests and its effect on natural enemies and plants" (in en). https://hero.epa.gov/hero/index.cfm/reference/details/reference_id/8600623. 
  14. ↑ Keum, Young-Soo; Kim, Jeong-Han; Kim, Yong-Whan; Kim, Kyun; Li, Qing X. (May 2002). "Photodegradation of diafenthiuron in water". Pest Management Science 58 (5): 496–502. doi:10.1002/ps.483. ISSN 1526-498X. PMID 11997978. https://pubmed.ncbi.nlm.nih.gov/11997978/. 
  15. ↑ Riaz-Ul-Haq, Muhammad; Javeed, Rabia; Iram, Saman; Rasheed, Muhammad Arslan; Amjad, Muhammad; Iqbal, Furhan (September 2018). "Effect of Diafenthiuron exposure under short and long term experimental conditions on hematology, serum biochemical profile and elemental composition of a non-target organism, Labeo rohita". Environmental Toxicology and Pharmacology 62: 40–45. doi:10.1016/j.etap.2018.06.006. ISSN 1872-7077. PMID 29957367. https://pubmed.ncbi.nlm.nih.gov/29957367/#:~:text=Diafenthiuron%20is%20a%20thiourea%20compound,potential%20threat%20for%20aquatic%20life. 
  16. ↑ 16.0 16.1 Arney, Malcolm (1996) (in English). Diafenthiuron. National registration authority. 
  17. ↑ Gao, Y.-N (September 2010). "Risk assessment of diafenthiuron to three species of aquatic organisms". Journal of Ecology and Rural Environment 26 (5): 487–491. https://www.researchgate.net/publication/288438615. 
  18. ↑ Su, Menglan; Bao, Rongkai; Wu, Yaqing; Gao, Bo; Xiao, Peng; Li, Wenhua (May 2023). "Diafenthiuron causes developmental toxicity in zebrafish (Danio rerio)". Chemosphere 323: 138253. doi:10.1016/j.chemosphere.2023.138253. ISSN 1879-1298. PMID 36849025. Bibcode: 2023Chmsp.323m8253S. https://pubmed.ncbi.nlm.nih.gov/36849025/. 
  19. ↑ 19.0 19.1 Stanley, Johnson; Chandrasekaran, Subramanian; Preetha, Gnanadhas; Kuttalam, Sasthakutty (May 2010). "Toxicity of diafenthiuron to honey bees in laboratory, semi-field and field conditions". Pest Management Science 66 (5): 505–510. doi:10.1002/ps.1900. ISSN 1526-4998. PMID 20069631. https://pubmed.ncbi.nlm.nih.gov/20069631/. 
  20. ↑ Stuligross, Clara; Williams, Neal M. (2021-11-30). "Past insecticide exposure reduces bee reproduction and population growth rate". Proceedings of the National Academy of Sciences of the United States of America 118 (48): e2109909118. doi:10.1073/pnas.2109909118. ISSN 1091-6490. PMID 34810261. Bibcode: 2021PNAS..11809909S. 



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