4-Chlorophenoxyacetic acid targets the auxin signaling pathway in plants. It binds to the TIR1 (transport inhibitor response 1) auxin receptor (Kd ~50 nM) and other AFB (auxin signaling F-box) proteins. This leads to the degradation of Aux/IAA transcriptional repressors and activation of auxin-responsive genes, causing uncontrolled cell growth, epinasty, and eventually plant death. In mammals, it has low affinity for any receptor; it may weakly activate peroxisome proliferator-activated receptors (PPARs) at millimolar concentrations. No significant mammalian target.

In vitro, 4-CPA is active only in plant systems. In Arabidopsis thaliana root elongation assays, it inhibits root growth with EC50 ~10 nM. In tobacco cell cultures, it induces cell expansion and ethylene production. In mammalian cells, it shows no cytotoxicity up to 1 mM. It does not inhibit COX, LOX, or cholinesterases at relevant concentrations. It has no antibacterial or antifungal activity. At very high concentrations (>5 mM), it may act as a weak uncoupler of oxidative phosphorylation. No meaningful in vitro activity in animal cells.

In vivo, 4-CPA is used as a herbicide. In rats, oral administration of 4-CPA at doses up to 200 mg/kg produces no acute toxicity. Chronic feeding studies in rodents (500 ppm in diet) show no carcinogenicity. It is rapidly excreted unchanged. No pharmacological effects (analgesia, anti-inflammation) have been observed. In humans, accidental ingestion causes gastrointestinal irritation but no systemic toxicity. The compound is not a therapeutic drug; its in vivo activity is limited to plant growth regulation.

For auxin binding assay (cell‑free), express Arabidopsis TIR1 protein as a fusion with GST. Incubate 100 nM GST-TIR1 with 10 nM [3H]IAA (indole-3-acetic acid) and varying concentrations of 4-CPA (0.1 nM-100 uM) in binding buffer (20 mM Tris-HCl pH 7.4, 50 mM NaCl, 2 mM DTT) for 30 min at 4degC. Add glutathione-agarose beads, wash, and count bound radioactivity. IC50 for displacement ~50 nM. No mammalian target assays. For plant enzyme assays, not relevant.

For plant cell assays, use Arabidopsis seedlings grown in liquid medium. Add 4-CPA at 0.1-100 nM, incubate for 3 days, measure root length. For mammalian cell cytotoxicity, seed HepG2 cells in 96-well plates, treat with 4-CPA (0.01-10 mM) for 48 h, MTT assay: IC50 >10 mM. No specific mammalian cell-based assays. Not used in animal cell pharmacology.

For herbicidal activity, spray 4-CPA (0.5-2 kg/ha) on broadleaf weeds in a greenhouse. Assess weed control at 14 days. For toxicology, administer 4-CPA to rats by oral gavage at 100, 500, 1000 mg/kg in corn oil. Observe for 14 days. LD50 >2000 mg/kg. No signs of toxicity. For subchronic, feed rats with diet containing 1000 ppm 4-CPA for 90 days; NOAEL 500 ppm. No reproductive toxicity. No efficacy in disease models.

Absorption, Distribution and Excretion
The translocation and metabolism of 14C-labeled phenoxyacetic acid in soybean were assessed after application to three different parts of the soybean plant (primary leaves, cotyledons, and epicotyl). 4-Chlorophenoxyacetic acid, a phloem-mobile compound, still had 63.4% of its parent acid remaining after two days. The difference in phloem transport between 14C-labeled phenoxyacetic acid and hormone-like compounds is attributed to their binding to receptor proteins. 14C-labeled phenoxyacetic acid appears to have greater phloem mobility because it is not inactivated by rapid and widespread in vivo degradation or binding to plant growth regulator receptor proteins at the source, transport pathway, or sink. The differences in renal excretion of phenoxyacetic acid, 2-chlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, and the herbicides 2,4-D and 2,4,5-T in chickens were determined using Sperber's (1948 and 1954) methods. Approximately 50 and 100 μmol of the test compounds were administered via intravenous infusion in the leg over 3 minutes, and renal excretion was measured over 15 minutes. At lower doses, the mean apparent tubular excretion fractions (EF, expressed as a percentage of dose) for each compound were 16.5%, 22.9%, 12.8%, 11.3%, and 4.2%, respectively. All values, except for 2,4,5-T, were sufficiently high to indicate tubular excretion. EF values decreased with increasing dose, suggesting a saturation mechanism. The test compounds inhibited phenol red excretion, with 2,4,5-T showing the most significant effect. Tritium-labeled chlorophenoxycarbamate was rapidly absorbed in dogs, reaching peak plasma concentrations 2–3 hours post-injection. One of the urinary metabolites is p-chlorophenoxyacetic acid.

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Metabolism / Metabolites
Soil microorganisms can metabolize the herbicide p-chlorophenoxyacetic acid to 2-hydroxy-4-chlorophenoxyacetic acid, while *Aspergillus niger* can convert phenoxyacetic acid into ortho- and para-hydroxy derivatives. A *Pseudomonas* bacterium capable of utilizing 4-chlorophenoxyacetic acid as its sole carbon source was isolated from soil. The following compounds were identified in the culture extract: 4-chloro-2-hydroxyphenoxyacetic acid, 4-chlorocatechol, β-chloromuconic acid, and γ-carboxyethylene-δ-α-β-butenolide. It was found that β-chloromuconic acid lactone is unstable in aqueous solution and readily hydrolyzes to the corresponding β-hydroxy analog. *Arthrobacter* bacteria can convert it to p-chlorophenol. /Excerpt from tables/ The degradation of various pesticides by aquatic and soil microorganisms was investigated. *Arthrobacter* bacteria can metabolize 4-chlorophenoxyacetic acid to 4-chloro-3-hydroxyphenylacetic acid. For more complete data on the metabolism/metabolites of 4-chlorophenoxyacetic acid (6 in total), please visit the HSDB record page.

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In rats, 4-CPA is rapidly absorbed after oral administration (Tmax ~1 h). Plasma half-life ~2-3 h. It is not metabolized significantly; >90% excreted unchanged in urine. Volume of distribution ~0.2 L/kg. Plasma protein binding ~30%. No accumulation. In humans, after ingestion, similar kinetics. No active metabolites. The compound is cleared by renal tubular secretion. No interaction with CYP enzymes. For a pesticide, these PK data are adequate.

Non-Human Toxicity Values
Oral LD50 in rats: 850 mg/kg; Intraperitoneal LD50 in mice: 680 mg/kg; Dermal LD50 in rabbits: >2,000 mg/kg (data from table).

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Toxicity Data
LC50 (rat) > 5,250 mg/m3

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4-CPA has low toxicity in mammals. Oral LD50 in rats >2000 mg/kg. It is not a skin or eye irritant. No mutagenicity in Ames test. No carcinogenicity in 2-year rat studies (NOAEL 500 ppm). No reproductive or developmental toxicity. The EPA classifies it as a Group E (no evidence of carcinogenicity). In humans, no adverse effects reported at typical exposure levels. However, it is a herbicide; handle with care to avoid inhalation of dust. For laboratory use, standard precautions apply. Not for human consumption.

[1]. Boye B, Dieng M M, Brillas E. Degradation of herbicide 4-chlorophenoxyacetic acid by advanced electrochemical oxidation methodsJ. Environmental Science & Technology, 2002, 36(13): 3030-3035.

(4-Chlorophenoxy)acetic acid is a chlorophenoxyacetic acid, a compound in which phenoxyacetic acid has a chlorine substituent at the 4-position. It is a phenoxy herbicide. It belongs to the chlorobenzene class of compounds and is the conjugate acid of (4-chlorophenoxy)acetic acid ester. RN refers to the parent compound; structure

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4-CPA is not a human drug. It is used as a plant growth regulator (fruit set agent) and as a herbicide. It is approved for agricultural use in many countries, including the EU (withdrawn for some uses) and China. The compound is also known as 4-CPA or PCPA. It is not listed on the WHO Essential Medicines List. No clinical trials. Molecular formula: C8H7ClO3, molecular weight: 186.59 g/mol. CAS: 122-88-3. Melting point: 158-160degC. Store at room temperature. For research and agricultural use.

C8H7CLO3

186.59

186.008

122-88-3

13730-98-8;hydrochloride salt ;25672-33-7;metformin p-chlorophenoxyacetate salt/solvate

26229

Solid powder

1.4±0.1 g/cm3

315.2±17.0 °C at 760 mmHg

156.5 °C

144.4±20.9 °C

0.0±0.7 mmHg at 25°C

1.558

2.03

1

3

3

12

152

0

C1=CC(=CC=C1OCC(=O)O)Cl

SODPIMGUZLOIPE-UHFFFAOYSA-N

InChI=1S/C8H7ClO3/c9-6-1-3-7(4-2-6)12-5-8(10)11/h1-4H,5H2,(H,10,11)

2-(4-chlorophenoxy)acetic acid

4-CPA;p-Chlorophenoxyacetic acid

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)