Indole-3-acetic acid
Names | |
---|---|
Preferred IUPAC name
(1H-Indol-3-yl)acetic acid | |
Other names
Indole-3-acetic acid,
indolylacetic acid, 1H-Indole-3-acetic acid, indoleacetic acid, heteroauxin, IAA | |
Identifiers | |
3D model (
JSmol ) |
|
ChEBI | |
ChEMBL | |
ChemSpider | |
DrugBank | |
ECHA InfoCard
|
100.001.590 |
KEGG | |
PubChem CID
|
|
UNII | |
CompTox Dashboard (EPA)
|
|
| |
| |
Properties | |
C10H9NO2 | |
Molar mass | 175.187 g·mol−1 |
Appearance | White solid |
Melting point | 168 to 170 °C (334 to 338 °F; 441 to 443 K) |
insoluble in water. Soluble in ethanol to 50mg/ml | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
Indole-3-acetic acid (IAA, 3-IAA) is the most common naturally occurring plant hormone of the auxin class. It is the best known of the auxins, and has been the subject of extensive studies by plant physiologists.[1] IAA is a derivative of indole, containing a carboxymethyl substituent. It is a colorless solid that is soluble in polar organic solvents.
Biosynthesis
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 start from tryptophan, but there is also a biosynthetic pathway independent of 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 thaliana.[5]
In rats, IAA is a product of both endogenous and colonic microbial metabolism from dietary
Biological effects
As all auxins, IAA has many different effects, such as inducing cell elongation and cell division with all subsequent results for plant growth and development. On a larger scale, IAA serves as signaling molecule necessary for development of plant organs and coordination of growth.
Plant gene regulation
IAA enters the plant cell nucleus and binds to a protein complex composed of a ubiquitin-activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), and a ubiquitin ligase (E3), resulting in ubiquitination of Aux/IAA proteins with increased speed.[11] Aux/IAA proteins bind to auxin response factor (ARF) proteins, forming a heterodimer, suppressing ARF activity.[12] In 1997 it was described how ARFs bind to auxin-response gene elements in promoters of auxin regulated genes, generally activating transcription of that gene when an Aux/IAA protein is not bound.[13]
IAA inhibits the photorespiratory-dependent cell death in photorespiratory catalase mutants. This suggests a role for auxin signalling in stress tolerance.[14]
Bacterial physiology
IAA production is widespread among environmental bacteria that inhabit soils, waters, but also plant and animal hosts. Distribution and
Fungal symbiosis
Fungi can form a fungal mantle around roots of perennial plants called
Skatole biosynthesis
Skatole, the odorant in feces, is produced from tryptophan via indoleacetic acid. Decarboxylation gives the methylindole.[19][20]
Synthesis
Chemically, it can be synthesized by the reaction of indole with glycolic acid in the presence of base at 250 °C:[21]
Alternatively the compound has been synthesized by Fischer indole synthesis using glutamic acid and phenylhydrazine.[22] Glutamic acid was converted to the necessary aldehyde via Strecker degradation.
Many methods for its synthesis have been developed since its original synthesis from indole-3-acetonitrile.[23]
History and synthetic analogs
William Gladstone Tempelman studied substances for growth promotion at Imperial Chemical Industries Ltd. After 7 years of research he changed the direction of his study to try the same substances at high concentrations in order to stop plant growth. In 1940 he published his finding that IAA killed broadleaf plants within a cereal field.[24]
The search for an acid with a longer half life, i.e. a metabolically and environmentally more stable compound led to
Other less expensive synthetic auxin analogs on the market for use in horticulture are indole-3-butyric acid (IBA) and 1-naphthaleneacetic acid (NAA).[26]
Mammalian toxicity/health effects
Little research has been conducted on the effects of IAA on humans and toxicity data are limited. No data on human carcinogenic, teratogenic, or developmental effects have been created.
IAA is listed in its
Developmental toxicity
IAA produces microcephaly in rats during the early stage of cerebral cortex development. IAA treatment of pregnant rats, at a dose of 1 gram per kg of body weight per day, decreased the locomotor activities of rat embryos/fetuses; treatment with IAA and analog 1(methyl)-IAA resulted in apoptosis of neuroepithelial cell and significantly decreased brain sizes relative to body weight in embryonic rats.[33]
Immunotoxin
IAA is an
In 2002 it had been hypothesized that IAA coupled with horseradish peroxidase (HRP) could be used in targeted cancer therapy. Radical-IAA molecules would attach to cells marked by HRP and HRP reactive cells would be selectively killed.[35] In 2010 in vitro experiments proved this concept of IAA as an immunotoxin when used in preclinical studies of targeted cancer therapy, as it induced apoptosis in bladder[34] and in hematological malignancies.[36]
References
- PMID 21421392.
- PMID 20192736.
- PMID 22025724.
- PMID 22025721.
- PMID 19279202.
- PMID 1117200.
- PMID 26469515.
- PMID 13610897.
- S2CID 221402986.
- S2CID 221179265.
- S2CID 24159190.
- PMID 14742873.
- PMID 9188533.
- PMID 26317137.
- S2CID 22123626.
- PMID 26347301.
- PMID 26231639.
- PMID 26179718.
- PMID 18223109.
- PMID 367144.
- ^ Johnson, Herbert E.; Crosby, Donald G. (1964). "Indole-3-acetic Acid". Organic Syntheses. 44: 64; Collected Volumes, vol. 5, p. 654.
- .
- .
- .
- .
- ^ "PGR Planofix - Crop Science India". www.cropscience.bayer.in. Retrieved 2022-04-28.
- ^ "1H-Indole-3-acetic acid" Registry of Toxic Effects of Chemical Substances (RTECS). Page last updated:November 8, 2017.
- ^ "Indole-3-Acetic Acid: Material Safety Data Sheet." November 2008.
- S2CID 45619222. Retrieved 2020-01-08.
- PMID 31484323.
- PMID 25145928.
- PMID 34667167.
- PMID 16141651.
- ^ PMID 20225657.
- PMID 12052213.
- PMID 24578503.