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DL-Phosphinothricin

Names
IUPAC name Ammonium (2-amino-4-(methylphosphinato)butanoate
Other names Glufosinate ammonium; 2-Amino-4-(hydroxymethylposphinyl)butanoic acid monoammonium salt; Phosphinothricin
Identifiers
CAS Number	77182-82-2
3D model (JSmol)	Interactive image
PubChem CID	53597
SMILES CP(=O)(CCC(C(=O))N)O.
Properties
Chemical formula	C5H15N2O4P
Molar mass	198.159 g·mol
Appearance	white crystalline powder
Melting point	205 °C (401 °F; 478 K)
Boiling point	Not measurable due to thermal decomposition in the range 245–305 °C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is  ?) Infobox references

DL-Phosphinothricin is a broad-spectrum herbicidal ammonium salt (a derivative of glufosinate) with the chemical formula C₅H₁₅N₂O₄P. It is a potent inhibitor to the enzyme glutamine synthetase, which is central to nitrogen regulation in various plant cell types, thus making it a highly effective compound in many nonselective systemic herbicides. DL-Phosphinothricin irreversibly inhibits glutamine synthetase, an enzyme necessary for the production of glutamine and for ammonia detoxification. DL-Phosphinothricin use in plants leads to reduced glutamine levels and elevated ammonia levels in tissues, halting photosynthesis, resulting in plant death. (http://www.pan-uk.org/pestnews/Actives/glufosin.htm)

History

DL-phosphinothricin is typically used in three different situations as an herbicide:

• directed sprays for weed control
• use as a crop desiccant to facilitate the harvest
• use in genetically modified DL-phosphinothricin-resistant crops

Most DL-phosphinothricin use within the United States is with genetically modified crops in industrial farming.

History and Use of Phosphinothricin-Resistant Crops

Glufosinate-resistance was first commercialized in canola in 1995 and has since been commercialized in other crops such as corn, cotton and soybeans. 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 L-phosphinothricin acetyltransferases that catalyze N-acetylation of glufosinate.

Sales of the glufosinate-resistant corn started in 1997. Commercial corn lines use both bar and pat genes in the transformation process.

Production

Properties and Chemistry

DL-Phosphinothricin has a molecular formula of C₅H₁₅N₂O₄P. Its broad-spectrum herbicidal properties control important weeds such as morning glories, hemp sesbania (Sesbania bispinosa), Pennsylvania smartweed (Polygonum pensylvanicum) and yellow nutsedge better than a formerly used, less broad-spectrum herbicide, glyphosate. DL-Phosphinothricin is a contact herbicide, and is applied to young plants during early development for full effectiveness.

Biochemistry

DL-phosphinothricin is a component of the tripeptide bialaphos from Streptomyces viridochromeogenes. Bialaphos is hydrolyzed to L-phosphinothricin which directly acts as the irreversible inhibitor of glutamine synthetase. The buildup of ammonia after application is measurable after 1h of treatment.

Human Exposure Sources

Exposure to Humans in the Environment

DL-phosphinothricin is found in many industrial, recreational and public areas, such as airports, schools, parking lots and railroads. Common areas that it is used include around the base of shrubs, in sand traps on gold courses, around fences, and around sign posts. The herbicide is also used around ornamental plants, Christmas tree plantations, and fruit and nut orchards and vineyards.

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 common foods include potatoes, peas, beans, corn, wheat, and barley. The chemical can also be passed to humans that ingest animals who are fed contaminated straw. 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 and organic matter content

Exposure Limits

There are no exposure limits established by the Occupational Safety & Health Administration (OSHA) or the American Conference of Governmental Industrial Hygienists (ACGIH).

Toxicity

The Globally Harmonized System Classification and Labeling of Chemicals (GHS) have classified DL-Phosphinothricin into three categories:

• H302 - Acute toxicity, Oral (category 4)
• H302 - Acute toxicity, Inhalation (Category 4)
• H361 - Reproductive toxicity (Category 2).

Reproductive Toxicity

DL-Phosphinothricin is a suspected human reproductive toxicant.

Overexposure Symptoms

Irritation, itching, GI upset, nausea, headache, respiration difficulties, depression, blood pressure fluctuations, convulsions, excessive salivation, coma, cyanosis, kidney malfunction, central nervous system stimulation, and in extreme cases, death.

Target Organs

Respiratory system, gastrointestinal system, central nervous system, kidney, blood. Routes of entry include via ingestion, inhalation, skin or eye contact.

General

Liberty herbicide has a similar structure to the amino acid glutamic acid. This natural amino acid stimulates the human central nervous system, and can cause death of nerve cells of the brain when experienced in excess. In humans glufosinate ammonium (the component of liberty similar to glutamic acid) poisoning leads to unconsciousness, convulsions, respiratory disease, and potentially kidney disorders. This would occur if one were to come into contact with a large amount of the herbicide, and it is unknown if the accumulation of the herbicide in GM crops could accumulate to create a response such as those associated with poisoning. Further more, little is known about the chronic or longer term effects associated with low dose exposure to genetically modified crops grown using liberty.

Health Effects

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Eating genetically modified corn on which the liberty herbicide was used may lead to inactive herbicide entering your gut. Through the digestion process this can reactivate and cause a toxic reaction. The herbicide itself is derived from a natural antibiotic produced by soil bacterium; in order to ensure the actual bacteria aren’t killed by the antibiotic they are producing, they produce the enzymes which convert the antibiotic to a non toxic form known as N-acetly-L-glufosinate (also known as NAG). Two genes within the bacteria are accountable for the enzymatic proteins produces, and BC crops have these genes inserted into their DNA, making them unsusceptible to the herbicide when it is used on them as the plants then produce the enzyme. When liberty is strayed glufosinate ammonium is transported throughout the plant, and the enzymes convert it to NAG. As the form is no longer toxic, the genetically modified crop continues to live whilst all other plants that have not been genetically modified in the same way die. However, the NAG still remains within in the plants and only continues to accumulate, as more herbicide is used- we are eating NAG in the food we consume. In our digestive system it can be converted back to its toxic herbicide form. Gut bacteria may be responsible for this reconversion, and unfortunately, the herbicide may go on to kill our healthy gut bacteria as well.

Environmental Effects and Issues

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One of the basic and very important traits incorporated into genetically modified (GW) crops is their ability to resist herbicide effects (they have a certain herbicide tolerance). 71% of crops are specifically engineered to resist the herbicides liberty and roundup. By creating the herbicide tolerance in genetically modified crops means that the crop can survive he use of the herbicide but no other weeds, bacteria, fungi, etc., can, and therefore the GM crop and herbicide work hand in hand to grow as efficiently as possible and produce an abundant crop. This also is a moneymaking industry; when a farmer choses to use a herbicide tolerant GM seed, they have to purchase the company’s herbicide as well. Corn, soy, cotton, and canola are the major GM crops grown in the United States; all four come in Liberty and Roundup tolerant strains. Liberty herbicide and certain lines of genetically modified corn are created in conjunction with one another; this is the method to creating herbicide tolerant crops. When Herbicide tolerant seeds are purchased the farmers must also purchase the herbicide with them. Ultimately this increases the amount of herbicide used on the herbicide tolerant crops. Currently, no safety testing is required for herbicide tolerant crops if they are deemed fit for consumption by biotech companies; the FDA has nothing more to add on this testing either, but many remain weary of liberties potential side effects. While it is to be used on weeds and plants, it has negative effects on bacteria, fungi, insects, humans, and animals as well.

US Regulation

Glufosinate ammonium is a United States Environmental Protection Agency (US EPA) registered chemical. It is also a California registered chemical. The US Environmental Protection Agency (US EPA) classifies the chemical as 'persistent' and 'mobile'. As noted above, there are no exposure limits established by the Occupational Safety & Health Administration (OSHA) or the American Conference of Governmental Industrial Hygienists (ACGIH).

Food Standards

The Food and Agriculture Organization of the United Nations (FAO) and World Health Organization (WHO) have a standard list of maximum residue limits for glufosinate-ammonium.

Tolerances

The United States Government has provided a list of the tolerances established for residues of the herbicide glufosinate ammonium in its Code of Federal Regulations.

References

This section is empty. You can help by adding to it. (March 2015)

References

1. Caspi; et al. (August 2009). "MetaCyc Compound Class: phosphinothricin". "MetaCyc" Compound Class: phosphinothricin. SRI International Pathway Tools version 19.0. Retrieved March 2015. {{cite web}}: Check date values in: |accessdate= (help); Explicit use of et al. in: |last= (help)
2. ^ 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)
3. ^ Fox (1996). "Herbicide Factsheet Glufosinate". Journal of Pesticide Reform, Vol 16, No. 4. Retrieved March 2015.
4. ^ http://www.pan-uk.org/pestnews/Actives/glufosin.htm
5. ^ http://phytotechlab.com/media/downloads/7382/P679MSDS.pdf
6. https://www.organicconsumers.org/scientific/genetically-engineered-crops-may-produce-herbicide-inside-our-intestines
7. https://www.organicconsumers.org/scientific/genetically-engineered-crops-may-produce-herbicide-inside-our-intestines
8. https://www.organicconsumers.org/scientific/genetically-engineered-crops-may-produce-herbicide-inside-our-intestines
9. http://www.codexalimentarius.net/pestres/data/pesticides/details.html?id=175
10. http://www.ecfr.gov/cgi-bin/text-idx?node=se40.24.180_1473&rgn=div8

Further reading

• Basta technical guide
• Jewell, Topsy (1998). "Glufosinate ammonium fact sheet". Pesticides News. Archived from the original on 2008-08-01. Retrieved 2007-10-20. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)

• Ammonium compounds
• Herbicides
• Phosphinic acids