Clopyralid's mechanism of action involves disrupting the plant's auxin signaling pathway, which is responsible for regulating cell division and elongation. It mimics natural plant hormones (auxins), leading to uncontrolled growth and eventual plant death. The compound is a synthetic auxin herbicide that selectively inhibits the growth of broadleaf weeds over non-broadleaf plant species. It belongs to the picolinic acid family of herbicides, which also includes aminopyralid, picloram, triclopyr, and several less common herbicides.

In vitro, clopyralid's herbicidal activity is assessed by measuring its effects on plant cell growth and auxin signaling. Plant cell cultures or excised plant tissues are treated with various concentrations of clopyralid, and the inhibition of cell elongation and division is measured. The compound's ability to mimic auxin can be assessed using auxin-responsive reporter genes in transgenic plants. Specific IC50 values for growth inhibition are not detailed in the provided search results.

In vivo, clopyralid is applied as a foliar spray in field or greenhouse trials. The compound is formulated as an emulsifiable concentrate or wettable powder and applied at recommended rates. Efficacy is evaluated by assessing weed control (percentage of weed coverage or biomass reduction) at regular intervals after application. Crop safety is assessed by measuring crop plant growth and yield. Clopyralid is particularly effective against thistles and clovers, and it is the only effective herbicide available for controlling creeping thistle in some regions.

The in vitro activity of clopyralid is assessed using plant cell cultures or excised plant tissues. Plant cells are cultured in appropriate media and treated with various concentrations of clopyralid (typically 0.1-100 µM). Cell growth is assessed by measuring cell number or biomass. The effect on auxin signaling can be assessed using auxin-responsive reporter genes or by measuring the expression of auxin-regulated genes by qPCR. The inhibition of root elongation or shoot growth can be assessed in seedling-based assays.

For cellular assays, plant cell cultures (e.g., Arabidopsis thaliana cell suspension cultures) or seedling tissues are used. Cells or tissues are treated with various concentrations of clopyralid for defined periods. Cell viability is assessed using standard assays such as Evans blue staining or fluorescein diacetate staining. The expression of auxin-responsive genes is analyzed by qPCR. The effect on cell division and elongation is assessed by microscopy.

In vivo, clopyralid is applied as a foliar spray in field or greenhouse trials. The compound is formulated as an emulsifiable concentrate or wettable powder and applied at recommended rates (typically 0.1-0.5 kg active ingredient per hectare). Efficacy is evaluated by visually assessing weed control (percentage of weed coverage or biomass reduction) at regular intervals after application. Crop safety is assessed by measuring crop plant growth and yield. In toxicological studies, clopyralid is administered to animals, and various toxicity endpoints are assessed.

Absorption, Distribution and Excretion
This study compared the absorption and translocation patterns of commercially available 14C chloropyridine in the forms of monoethanolamine, potassium salt, 2-ethylhexyl ester, and 1-decyl ester in Cirsium arvense and Polygonum convolvulus under three different environmental conditions. Plants were grown in silica sand with a water content of 33% (w/w) at 35% or 65% relative humidity, or under water stress at 65% relative humidity. Approximately 26%, 39%, 86%, 93%, and 100% of the applied amount were recovered after 72 hours of application to glass coverslips in the growth chamber, respectively. However, after applying five formulations to two plants, only 2-ethylhexyl ester showed a significant loss of 14C radioactivity. Acids were the most readily absorbed formulations regardless of environmental conditions. Salts and esters had lower absorption rates compared to acids. When data were expressed as a percentage of absorbed radioactivity, there was no significant difference in translocation among acids, monoethanolamine salts, and potassium salts. However, the amount of absorbed 2-ethylhexyl ester and 1-decyl ester exported from treated leaves was significantly reduced. These results suggest that once absorbed, esters are not easily separated from the cuticle, while acids and both salts enter the symptomometrium for subsequent translocation. Comparison of results under three environmental conditions revealed that under low humidity or water stress, the absorption of monoethanolamine and potassium salts was significantly reduced, while the absorption of acids and esters remained unaffected. Five Cr1:CD (F-344) BR rats (half male and half female) were used in each group. One group received a single intravenous injection (5 mg/kg, dissolved in saline) or a single gavage administration (5 mg/kg or 150 mg/kg) of 14C-labeled clopyridine. Another five rats (half male and half female) received 5 mg/kg/day of unlabeled clopyridine daily for 14 days, followed by a single 5 mg/kg/day administration of 14C-labeled clopyridine. No marker was detected in exhaled breath. Animals were sacrificed after 72 hours. Marker levels in tissues of all treatment groups were extremely low (carcass or stomach) or undetectable. Typically, regardless of the route of administration, over 90% of the marker was detected in urine collected within 24 hours. Small amounts of marker (1-5%) were detected in feces. Analysis of the only detectable marker in urine revealed it to be unmodified clopyridine.

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Metabolism/Metabolites
Five Cr1:CD (F-344) BR rats (half male and half female) were used in each group. One group received a single intravenous injection (5 mg/kg, dissolved in saline) or a single gavage administration (5 mg/kg or 150 mg/kg) of (14)C-labeled clopyridine. Another five rats (half male and half female) received 5 mg/kg/day of unlabeled clopyridine daily for 14 days, followed by a single administration of 5 mg/kg/day of (14)C-labeled clopyridine. No markers were detected in exhaled breath. After euthanasia at 72 hours, marker levels in tissues of all treatment regimens were extremely low (carcass or stomach) or undetectable. Typically, over 90% of the markers were detected in urine collected within 24 hours, regardless of the route of administration. Small amounts of markers (1-5%) were detected in feces. Analysis of the only detectable marker in urine revealed it to be unchanged clopyridine acid.
Clopyralid has a molecular weight of 192.00 g/mol and a molecular formula of C6H3Cl2NO2. It is a white to off-white crystalline solid with low water solubility but good solubility in organic solvents. The compound should be stored in a cool, dry place away from direct sunlight. Specific pharmacokinetic parameters are not detailed in the provided search results.

Toxicity Data
LC50 >1000 mg/m3 Non-human Toxicity Values LD50 Rat (Male) Oral: 4300 mg/kg LD50 Rat (Intraperitoneal): 900 mg/kg LD50 Rabbit (Dermal): >2000 mg/kg LD50 Mouse (Oral): >5000 mg/kg
Clopyralid has low acute toxicity in mammals, with oral LD50 values of >5000 mg/kg in rats. It can cause skin and eye irritation upon contact. The compound is toxic to aquatic organisms and should be used with caution near water bodies. In agricultural settings, proper personal protective equipment should be used during handling and application. The compound's use is regulated, and maximum residue limits are established for food commodities.

Chlorpyridine is an organochlorine pesticide with the structure 3,6-dichloropyridinecarboxylic acid. It is a herbicide belonging to the pyridine-based organochlorine pesticide class and is functionally related to pyridinecarboxylic acids. Chlorpyridine is a selective herbicide used to control broadleaf weeds, particularly thistle and clover. Chlorpyridine belongs to the pyridinecarboxylic acid class of herbicides, which also includes aminopyridine, chlorpyrifos, trichloropyridineoxyacetic acid, and some less common herbicides. Chlorpyridine is one of the few effective herbicides for controlling the perennial harmful weed Cirsium arvense. It is particularly damaging to peas, tomatoes, and sunflowers, and can render potatoes, lettuce, and spinach inedible. It is harmless to grasses. Mechanism of Action: A selective systemic herbicide, absorbed through leaves and roots, transported upwards and downwards, and accumulated in meristematic tissues. It exhibits an auxin-like response. It acts on cell elongation and respiration.
Clopyralid is a widely used herbicide in agriculture, particularly for weed control in cereals, pastures, and turf. Its selectivity for broadleaf weeds over grasses makes it a valuable tool in integrated weed management programs. Clopyralid is also used in combination with other herbicides for broader spectrum weed control. Its use is regulated by environmental protection agencies, and it is subject to ongoing review for safety and environmental impact.

C6H3CL2NO2

191.995

190.954

1702-17-6

15553

White crystalline solid
Colorless crystals

1.6±0.1 g/cm3

323.7±37.0 °C at 760 mmHg

151-152°C

149.6±26.5 °C

0.0±0.7 mmHg at 25°C

1.606

1.3

1

3

1

11

165

0

ClC1C([H])=C([H])C(=NC=1C(=O)O[H])Cl

HUBANNPOLNYSAD-UHFFFAOYSA-N

InChI=1S/C6H3Cl2NO2/c7-3-1-2-4(8)9-5(3)6(10)11/h1-2H,(H,10,11)

3,6-dichloropyridine-2-carboxylic acid

XRM-3972; XRM 3972; Clopyralid

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)

DMSO : ~100 mg/mL (~520.83 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (13.02 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (13.02 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
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.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (13.02 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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