View source for Malachite green

{{chembox
| Watchedfields = changed
| verifiedrevid = 303031553
| ImageFile =Malachite_green.svg 
| ImageSize = 
| IUPACName = 4-[(4-dimethylaminophenyl)phenyl-methyl]-''N'',''N''-dimethylaniline
| OtherNames = Aniline green; Basic green 4; Diamond green B; Victoria green B
| Section1 = {{Chembox Identifiers
|   CASNo_Ref = {{cascite}}
| CASNo =  569-64-2
|   PubChem = 11294
|   SMILES = [Cl-].CN(C)c1ccc(cc1)C(c2ccccc2)=C3C=CC(C=C3)=[N+](C)C
<!-- I'd almost rather write [Cl-].CN(C)c1ccc(cc1)[c+](c2ccccc2)c3ccc(cc3)N(C)C. Is there a way to represent fractional charge in SMILES? -->
|  ATCvet = yes
|  ATCCode_prefix = P53
|  ATCCode_suffix = AX16
  }}
| Section2 = {{Chembox Properties
|   Formula = C<sub>23</sub>H<sub>25</sub>ClN<sub>2</sub> (chloride)
|   MolarMass = 364.911 g/mol (chloride)
|   Appearance = 
|   Density = 
|   MeltingPt = 
|   BoilingPt = 
|   Solubility = 
  }}
| Section3 = {{Chembox Hazards
|   MainHazards = 
|   FlashPt = 
|   Autoignition = 
  }}
}}

'''Malachite green''' is an [[organic compound]] that is used as a [[dyestuff]] and has emerged as a controversial agent in [[aquaculture]].  Malachite green is traditionally used as a dye for materials such as [[silk]], [[leather]], and [[paper]].  Although called ''malachite green'', the compound is not related to the [[mineral]] [[malachite]] &mdash; the name just comes from the similarity of colour.

==Structures and properties==
Malachite Green is a member of the triphenylcarbenium salts, classified in the dyestuff industry as triarylmethane dyes. Formally, Malachite Green refers to the chloride salt [C<sub>6</sub>H<sub>5</sub>C(C<sub>6</sub>H<sub>4</sub>N(CH<sub>3</sub>)<sub>2</sub>)<sub>2</sub>]Cl, although the term Malachite Green is used loosely and often just refers to the coloured cation.  The [[oxalate]] salt is also marketed. The chloride and oxalate [[anion]]s have no effect on the color.  The intense green color of the cation results from an intense ([[extinction coefficient]] of 10<sup>5</sup> M<sup>−1</sup>cm<sup>−1</sup>) absorption band at 621&nbsp;nm.
{{pH_indicator_template|indicator_name=Malachite green (first transition)|low_pH=0.2 |high_pH=1.8 |low_pH_color=yellow |high_pH_color=00bb88}}
{{pH_indicator_template|indicator_name=Malachite green (second transition)|low_pH=11.5 |high_pH=13.2 |low_pH_color=00bb88 |high_pH_color=white}}
Malachite green is prepared by the condensation of [[benzaldehyde]] and [[dimethylaniline]] to give leuco malachite green (LMG):
:C<sub>6</sub>H<sub>5</sub>CHO  +  2 C<sub>6</sub>H<sub>5</sub>N(CH<sub>3</sub>)<sub>2</sub>  →   C<sub>6</sub>H<sub>5</sub>CH(C<sub>6</sub>H<sub>4</sub>N(CH<sub>3</sub>)<sub>2</sub>)<sub>2</sub>  +  H<sub>2</sub>O
Second, this colourless leuco compound, a relative of [[triphenylmethane]], is oxidized to the cation that is MG:
:C<sub>6</sub>H<sub>5</sub>CH(C<sub>6</sub>H<sub>4</sub>N(CH<sub>3</sub>)<sub>2</sub>)<sub>2</sub> + HCl  +  1/2 O<sub>2</sub>   →  [C<sub>6</sub>H<sub>5</sub>C(C<sub>6</sub>H<sub>4</sub>N(CH<sub>3</sub>)<sub>2</sub>)<sub>2</sub>]Cl  +  H<sub>2</sub>O
A typical oxidizing agent is [[manganese dioxide]].
[[Image:MalachiteGr&Leuco.png|thumb|left|638 px|Left is leuco-Malchite Green (LMG) and right are the two equivalent [[resonance structure]]s of the cation in MG.  In the carbinol derivative of MG is structurally related to LMG by replacement of the unique C-H by C-OH.]]

Hydrolysis of MG gives the carbinol form:<ref>Adina Raducan, Alexandra Olteanu, Mihaela Puiu, Dumitru Oancea "Influence of surfactants on the fading of malachite green" Central European Journal of Chemistry, 2008, Volume 6, pp 1895-1066 (Print) 1644-3624 (Online). {{DOI|10.2478/s11532-007-0066-0}}</ref>
:[C<sub>6</sub>H<sub>5</sub>C(C<sub>6</sub>H<sub>4</sub>N(CH<sub>3</sub>)<sub>2</sub>)<sub>2</sub>]Cl  +  H<sub>2</sub>O   →  C<sub>6</sub>H<sub>5</sub>C(OH)(C<sub>6</sub>H<sub>4</sub>N(CH<sub>3</sub>)<sub>2</sub>)<sub>2</sub>  +  HCl
This alcohol is important because it, not MG, traverses cell membranes. Once inside the cell, it is then metabolized into LMG. Only the cation MG is deeply coloured, whereas the LMG and carbinol derivatives are not.  This difference arises because only the cationic form has extended pi-delocalization, which allows the molecule to absorb visible light.

==Uses==
Malachite green is traditionally used as a dye.  Millions of kilograms of MG and related triarylmethane dyes are produced annually for this purpose.<ref>Thomas Gessner and Udo Mayer "Triarylmethane and Diarylmethane Dyes" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim.{{DOI|10.1002/14356007.a27_179}}</ref>

MG is active against the [[oomycete]] [[Saprolegnia]], which infects fish eggs in commercial aquaculture.  It is also a very popular treatment against [[ichthyophthirius]] in [[freshwater]] [[aquarium|aquaria]].  The principal metabolite, LMG, is found in fish treated with malachite green, and this finding is the basis of controversy and government regulation.

===Niche uses===
Numerous niche applications exploit the intense colour of MG. It is used as a [[staining|biological stain]] for [[microscopy|microscopic]] analysis of [[cell biology]] and [[histology|tissue samples]]. In the [[Gimenez stain|Gimenez staining method]], basic [[fuchsin]] stains bacteria red or magenta, and malachite green is used as a blue-green [[counterstain]]. Malachite green can also directly stain [[endospore]]s within cells; here a [[safranin]] counterstain is often used.  Malachite green can also be used as a [[saturable absorber]] in [[dye laser]]s, or as a [[pH indicator]] between pH 0.2 - 1.8. However this use is relatively rare.<!-- then why describe it-->  Leuco-malachite green (LMG) is used as a detection method for latent blood in [[criminalistics]].  [[Hemoglobin]] catalyzes the reaction between LMG and [[hydrogen peroxide]], converting the colorless LMG into malachite green.  Therefore, the appearance of a green color indicates the presence of [[blood]].<ref>[http://static.dna.gov/lab-manual/Linked%20Documents/Protocols/pdi_lab_pro_2.18.pdf Protocol 2.18 Leucomalachite Green Presumptive Test for Blood], ''National Forensic Science Technology Center'', July 8, 2010, Retrieved on July 8, 2010.</ref>

==Regulation==
In 1992 Canadian authorities determined that eating fish contaminated with malachite green posed a significant health risk.<ref>Wendy C. Andersen, Sherri B. Turnipseed, and José E. Roybal "Quantitative and Confirmatory Analyses of Malachite Green and Leucomalachite Green Residues in Fish and Shrimp" J. Agric. Food Chem. 2006, volume 54, pp 4517–4523.{{DOI|10.1021/jf0532258}} and references therein <!--delete and update this leading ref in future--></ref> Malachite green was classified a Class II Health Hazard. Due to its low manufacturing cost, malachite green is still used in certain countries with less restrictive laws for non-[[aquaculture]] purposes. In 2005, analysts in [[Hong Kong]] found traces of malachite green  in [[eel]]s and fish imported from [[China]] and [[Taiwan]]. In 2006 the United States [[Food and Drug Administration]] (FDA) detected malachite green in seafood imported from China, where the substance is also banned for use in aquaculture. In June 2007, the FDA blocked the importation of several varieties of seafood due to continued malachite green contamination.<ref>[http://www.usatoday.com/money/industries/food/2007-06-28-fish-cover-usat_N.htm Chinese fish crisis shows seafood safety challenges], ''USA Today'', 7/1/2007</ref>  The substance has been banned in the United States since 1983 in food-related applications.  It is banned in the UK also.<ref>Veterinary Residues Committee. Annual Report on Surveillance for Veterinary Residues in Food in the UK for 2001, 2002, and 2003. http://www.vet-residues-committee.gov.uk/.</ref>

Aquatic animals [[metabolism|metabolize]] malachite green to its leuco form. Being non-polar, LMG is retained in [[catfish]] muscle longer (t<sub>1/2</sub> = 10 days) than is MG (<sub>1/2</sub> = 2.8 days).

==Toxicity==
The [[LD50]] (oral, mouse) is 80&nbsp;mg/kg.  Rats fed malachite green experience “a dose-related increase in liver [[DNA]] adducts” along with lung [[adenoma]]s. Leuco-malachite green causes an “increase in the number and severity of changes”. As leuco-malachite green is the primary metabolite of malachite green and is retained in fish muscle much longer, most intake of malachite green would be in the leuco form. During the experiment, rats were fed up to 543 ppm of leuco-malachite green, an extreme amount compared to the average 5 ppb discovered in fish. After a period of two years, an increase in lung adenomas in male rats was discovered but no incidences of liver tumors. Therefore it could be concluded that malachite green caused carcinogenic symptoms, but a direct link between malachite green and liver tumor was not established.<ref>{{cite journal | author = S.J. Culp et al. | journal = Mutation Research | year = 2002 | pages = 55–63 | doi = 10.1016/S0027-5107(02)00152-5 | title = Mutagenicity and carcinogenicity in relation to DNA adduct formation in rats fed leucomalachite green | volume = 506-507 | pmid = 12351145}}</ref>

==References==
<references/>
==Further reading==
* {{cite journal | author = Bongsup P. Cho et al.  | journal = Chem. Res. Toxicol. | volume = 16 | issue = 3 | pages = 285–294 | year = 2003 | title = Synthesis and Characterization of N-Demethylated Metabolites of Malachite Green and Leucomalachite Green | doi = 10.1021/tx0256679 | pmid = 12641428}}
* {{cite journal | author = S. M. Plakas, K. R. El Said, G. R. Stehly, W. H. Gingerich and J. H. Allen | journal = Can. J. Fish. Aquat. Sci. | volume = 53 | pages = 1427–1433 | year = 1996 | doi = 10.1139/cjfas-53-6-1427 | title = Uptake, tissue distribution, and metabolism of malachite green in the channel catfish (''Ictalurus punctatus'')}}
* Schoettger, 1970; Smith and Heath, 1979; Gluth and Hanke, 1983. Bills et al. (1977)
* {{cite journal | author = Steven C. DeFina, Thorsten Dieckmann | doi = 10.1002/jlcr.554 | title = Synthesis of selectively <sup>15</sup>N- or <sup>13</sup>C-labelled malachite green | year = 2002 | journal = Journal of Labelled Compounds and Radiopharmaceuticals | volume = 45 | pages = 241}}

==External links==
*[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15213768&dopt=Abstract U.S. National Institutes of Health]
*[http://www.chembio.uoguelph.ca/preuss/Historical%20UK%20perspective%20on%20MG.pdf University of Guelph]
*[http://www.cfsan.fda.gov/~frf/lib4363.html U.S. Food and Drug Administration]
*[http://www.advisorybodies.doh.gov.uk/com/malachit.htm U.K. Department of Health]
*[http://chemistry.tidalswan.com/index.php?title=Malachite_Green Wiki Article on Malachite Green]
* [http://www.tgw1916.net/video_pages/Spore.html Malachite green - endospore staining technique (video)]

[[Category:Triarylmethane dyes]]
[[Category:Staining dyes]]
[[Category:PH indicators]]
[[Category:Antifungals]]
[[Category:Veterinary medicine]]
[[Category:Aromatic amines]]

[[cs:Malachitová zeleň]]
[[de:Malachitgrün]]
[[es:Verde malaquita]]
[[fr:Vert malachite]]
[[ko:말라카이트 그린]]
[[it:Verde malachite]]
[[nl:Malachietgroen]]
[[ja:マラカイトグリーン]]
[[no:Malakittgrønn]]
[[pl:Zieleń malachitowa]]
[[pt:Verde malaquita]]
[[ro:Verde malachit]]
[[ru:Малахитовый зелёный]]
[[fi:Malakiittivihreä]]
[[sv:Malakitgrönt (veterinärmedicin)]]
[[tr:Malahit yeşili]]
[[zh:孔雀石綠]]
[[Category:2Fix]]