Indole-3-acetic acid

Indole-3-acetic acid
IUPAC name

2-(1H-indol-3-yl)acetic acid
Other names

Indole-3-acetic acid,
indolylacetic acid,
indoleacetic acid,
heteroauxin,
IAA
Identifiers
CAS number 87-51-4 Y
PubChem 802
ChemSpider 780 Y
DrugBank DB07950
KEGG C00954 Y
ChEBI CHEBI:16411 Y
ChEMBL CHEMBL82411 Y
Jmol-3D images Image 1
Properties
Molecular formula C10H9NO2
Molar mass 175.184
Appearance white solid
Melting point

168-170 °C (441-443 K)
Solubility in water moderate
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Indole-3-acetic acid, also known as IAA, is a heterocyclic compound that is a phytohormone called auxin. This colourless solid is native plant compound, potent and the most important auxin.[1] The molecule is derived from indole, containing a carboxymethyl group (acetic acid).

Biosynthesis and biological activity

Main article: Auxin

IAA is predominantly produced in cells of the apex (bud) and very young leaves of a plant. Plants can synthesize IAA by several independent biosynthetic pathways, four of them starts from tryptophan, but there is also biosynthetic pathway independent on tryptophan.[2] Plants mainly produce IAA from tryptophan through indole-3-pyruvic acid.[3][4] IAA is also produced from tryptophan through indole-3-acetaldoxime in Arabidopsis.[5]

IAA has many different effects, as all auxins do, such as inducing cell elongation and cell division with all subsequent results for plant growth and development. On larger scale, IAA serves as signaling molecule necessary for development of plant organs and coordination of growth.

There are less expensive and metabolically stable synthetic auxin analogs on the market for use in horticulture, such as indole-3-butyric acid (IBA) and 1-naphthaleneacetic acid (NAA).

Studies of IAA in the 1940s led to the development of the phenoxy herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Like IBA and NAA, 2,4-D and 2,4,5-T are metabolically and environmentally more stable analogs of IAA. However, when sprayed on broad-leaf dicot plants, they induce rapid, uncontrolled growth, eventually killing them. First introduced in 1946, these herbicides were in widespread use in agriculture by the middle of the 1950s.

Synthesis

Chemically, it can be synthesized by the reaction of indole with glycolic acid in the presence of base at 250 °C:[6]

Many methods for its synthesis have been developed since its original synthesis from indole-3-acetonitrile.[7]

References

  1. ^ Simon, S; Petrášek, P (2011). "Why plants need more than one type of auxin". Plant Science 180 (3): 454–460. doi:10.1016/j.plantsci.2010.12.007. PMID 21421392. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TBH-51S6X51-2&_user=625101&_coverDate=03%2F31%2F2011&_rdoc=8&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info(%23toc%235143%232011%23998199996%232867740%23FLA%23display%23Volume)&_cdi=5143&_sort=d&_docanchor=&_ct=20&_acct=C000031698&_version=1&_urlVersion=0&_userid=625101&md5=d1409d89eff55b90161ef75e1ff59679&searchtype=a. 
  2. ^ Zhao, Yunde (2010). "Auxin Biosynthesis and Its Role in Plant Development". Annual Reviews of Plant Biology 61: 49–64. doi:10.1146/annurev-arplant-042809-112308. 
  3. ^ Mashiguchi K, et al. (2011). "The main auxin biosynthesis pathway in Arabidopsis". Proc. Natl. Acad. Sci. U.S.A. 108 (45): 18512-18517. doi:10.1073/pnas.1108434108. PMID 22025724. 
  4. ^ Won C, et al. (2011). "Conversion of tryptophan to indole-3-acetic acid by TRYPTOPHAN AMINOTRANSFERASES OF ARABIDOPSIS and YUCCAs in Arabidopsis". Proc. Natl. Acad. Sci. U.S.A. 108 (45): 18518-18523. doi:10.1073/pnas.1108436108. PMID 22025721. 
  5. ^ Sugawara S, et al. (2009). "Biochemical analyses of indole-3-acetaldoxime-dependent auxin biosynthesis in Arabidopsis". Proc. Natl. Acad. Sci. U.S.A. 106 (13): 5430-5435. doi:10.1073/pnas.0811226106. PMID 19279202. 
  6. ^ Herbert E. Johnson and Donald G. Crosby (1973), "Indole-3-acetic Acid", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV5P0654 ; Coll. Vol. 5: 654 
  7. ^ R. Majima and T. Hoshino (1925). "Synthetische Versuche in der Indol-Gruppe, VI.: Eine neue Synthese von beta-Indolyl-alkylaminen". Berichte der deutschen chemischen Gesellschaft 58: 2042. doi:10.1002/cber.19250580917.