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Glufosinate

Names
IUPAC name (RS)-2-Amino-4-(hydroxy(methyl)phosphonoyl)butanoic acid
Other names Phosphinothricin
Identifiers
CAS Number	51276-47-2
3D model (JSmol)	Interactive image
ChEBI	CHEBI:52136
ChEMBL	ChEMBL450298
ChemSpider	4630
ECHA InfoCard	100.051.893
EC Number	257-102-5
KEGG	C05042
PubChem CID	4794
CompTox Dashboard (EPA)	DTXSID0043973
InChI InChI=1S/C5H12NO4P/c1-11(9,10)3-2-4(6)5(7)8/h4H,2-3,6H2,1H3,(H,7,8)(H,9,10)Key: IAJOBQBIJHVGMQ-UHFFFAOYSA-N InChI=1/C5H12NO4P/c1-11(9,10)3-2-4(6)5(7)8/h4H,2-3,6H2,1H3,(H,7,8)(H,9,10)Key: IAJOBQBIJHVGMQ-UHFFFAOYAF
SMILES O=P(O)(CCC(C(=O)O)N)C
Properties
Chemical formula	C5H12NO4P
Molar mass	181.128 g·mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

Glufosinate (also known as phosphinothricin and often sold as an ammonium salt) is a broad-spectrum systemic herbicide with the chemical formula C₅H₁₅N₂O₄P. It irreversibly inhibits glutamine synthetase, an enzyme necessary for the production of glutamine and for ammonia detoxification. Application of glufosinate to plants leads to reduced glutamine and elevated ammonia levels in tissues, halting photosynthesis, resulting in plant death. It is found in many non-selective systemic herbicides such as Basta, Rely, Finale, Ignite, Challenge, and Liberty.

Use

Glufosinate was discovered by scientists at Hoechst in the 1970s.

Glufosinate is a broad-spectrum herbicide that is used to control important weeds such as morning glories, hemp sesbania (Sesbania bispinosa), Pennsylvania smartweed (Polygonum pensylvanicum) and yellow nutsedge similar to glyphosate. It is applied to young plants during early development for full effectiveness. It is sold in formulations under brands including Basta, Rely, Finale, Challenge and Liberty.

Glufosinate is typically used in three situations as an herbicide:

• directed sprays for weed control, including in genetically modified crops
• use as a crop desiccation to facilitate harvesting

Glufosinate also has shown to provide some protection against various plant diseases, as it also acts to kill fungi and bacteria on contact.

Genetically modified crops

Most glufosinate is used within the United States is with genetically modified crops.

Glufosinate-resistance was first commercialized in canola in 1995 and has since been commercialized in other crops such as corn (1997), cotton (2004) and soybeans (2011). Utilizing the bar gene from Streptomyces hygroscopicus or the pat gene from Streptomyces viridochromeogenes, crops are transformed to resist the herbicidal properties of the chemical. The two genes encode highly homogenous phosphinothricin acetyltransferases that catalyze N-acetylation of glufosinate, converting it into a compound that does not inhibit glutamine synthetase. Use of the bar or pat genes produces a very high level of resistance to the herbicide throughout the plant's life.

Mode of action

Phosphinothricin is a glutamine synthetase inhibitor that binds to the glutamate site. Glufosinate-treated plants die due to a buildup of ammonia and corresponding decrease in pH in the thylakoid lumen, leading to the uncoupling of photophosphorylation. The uncoupling of photophosphorylation causes the production of reactive oxygen species, lipid peroxidation, and membrane destruction.

Phosphinothricin is produced by various species of actinomycetes as a component of non-ribosomally synthesized peptides, for example, the tripeptide bialaphos from Streptomyces viridochromeogenes. Bialaphos is hydrolyzed to L-phosphinothricin which directly acts as the irreversible inhibitor of glutamine synthetase (GS). Inhibition of this enzyme causes a buildup of ammonia (NH₃), one of its substrates. In chloroplasts, the resulting elevated level of ammonia has a toxic effect. Elevated levels of ammonia are detectable within one hour after application of Phosphinothricin.

Toxicity

Glufosinate was found to be toxic to reproduction and was included in a biocide ban proposed by the Swedish Chemicals Agency and approved by the European Parliament on January 13, 2009.

Exposure to humans in foods

As DL-phosphinothricin is often used as a pre-harvest desiccant, residues can also be found in foods that humans ingest. Such foods include potatoes, peas, beans, corn, wheat, and barley. In addition, the chemical can be passed to humans through animals who are fed contaminated straw. Flour processed from wheat grain that contained traces of DL-phosphinothricin was found to retain 10-100% of the chemicals' residues.

The herbicide is also persistent; it has been found to be prevalent in spinach, radishes, wheat and carrots that were planted 120 days after the treatment of the herbicide. Its persistent nature can also be observed by its half-life which varies from 3 to 70 days depending on the soil type and organic matter content. Residues can remain in frozen food for up to two years and the chemical is not easily destroyed by cooking the food item in boiling water. The EPA classifies the chemical as 'persistent' and 'mobile' based on its lack of degradation and ease of transport through soil.

Exposure limits

There are no exposure limits established by the Occupational Safety & Health Administration or the American Conference of Governmental Industrial Hygienists. The WHO/FAO recommended acceptable daily intake (ADI) for glufosinate is 0.02 mg/kg. The European Food Safety Authority has set an ADI of 0.021 mg/kg. The Acute reference dose (ARfD) for child-bearing women is 0.021 mg/kg.

Regulation

Glufosinate ammonium is a United States Environmental Protection Agency EPA registered chemical. It is also a California registered chemical. It is not banned in any country and it is not a PIC pesticide. There are no exposure limits established by OSHA or the American Conference of Governmental Industrial Hygienists.

References

1. ^ Topsy Jewell for Friends of the Earth (December 1998). "Glufosinate ammonium fact sheet". Pesticides News No.42. Retrieved March 2015. {{cite web}}: Check date values in: |accessdate= (help)
2. Donn, G and Köcher, H. Inhibitors of Glutamine Synthetase. Chapter 4 in Herbicide Classes in Development: Mode of Action, Targets, Genetic Engineering, Chemistry. Eds Peter Böger, Ko Wakabayashi, Kenji Hirai. Springer Science & Business Media, 2012 ISBN 9783642594168
3. "The agronomic benefits of glyphosate in Europe" (PDF). Monsanto Europe SA. February 2010. Retrieved 06/02/2013. {{cite web}}: Check date values in: |accessdate= (help)
4. ^ "Encyclopedia of Agriculture and Food Systems: 5-volume set - Google Books". Books.google.com. 2014-07-29. Retrieved 2015-04-25.
5. ^ Nandula, Vijay K (December 2010). "Glyphosate Resistance in Crops and Weeds: History, Development, and Management". John Wiley & Sons. Retrieved March 2015. {{cite web}}: Check date values in: |accessdate= (help)
6. Herbicide-Resistant Crops: Agricultural, Economic, Environmental, Regulatory ..., Stephen O. Duke
7. Summary of Herbicide Mechanism of Action, HRAC and WSSA
8. "Neue rechtliche Regelungen für Pflanzenschutzmittel auf EU-Ebene" (PDF). Bundesministerium für Ernährung, Landwirtschaft und Verbraucherschutz (BMELV). January 2000. Retrieved 2013-03-22.
9. "Interpretation of criteria for approval of active substances in the proposed EU plant protection regulation" (PDF). Swedish Chemicals Agency (KemI). 2008-09-23. Retrieved 2013-03-20.
10. "MEPs approve pesticides legislation". 2009-01-13. Retrieved 2013-02-22.
11. ^ Watts, Meriel. "Glufosinate Ammonium Monograph" (PDF). Pesticide Action Network Asia and the Pacific. Retrieved 20 April 2015.
12. ^ "Chemical Identification and Company Information : DL-Phosphinothricin, Monoammonium Salt" (PDF). Phytotechlab.com. Retrieved 2015-04-25.
13. The Rotterdam Convention on Prior Informed Consent (PIC)

External links

• Bayer's site of LibertyLink crops
• Basta technical guide
• Glufosinate in the Pesticide Properties DataBase (PPDB)
• Glufosinate-ammonium in the Pesticide Properties DataBase (PPDB)
• Glufosinate-P in the Pesticide Properties DataBase (PPDB)

• Herbicides
• Phosphinic acids
• Ammonium compounds