The primary target of cyanazine is the photosynthetic electron transport chain in susceptible plants. As a triazine herbicide, it inhibits photosystem II (PSII), blocking the electron transport chain and preventing the conversion of light energy into chemical energy. This leads to the accumulation of reactive oxygen species and ultimately plant death. The compound's selective activity is based on differential metabolism in target versus non-target plants.

Cyanazine has been shown to be non-genotoxic[1].

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In vitro activity of cyanazine is measured by its ability to inhibit photosynthetic electron transport. The compound binds to the D1 protein of the photosystem II reaction center, blocking electron flow from QA to QB. This inhibition can be measured using isolated chloroplasts or thylakoid membranes by monitoring oxygen evolution or chlorophyll fluorescence. These in vitro assays demonstrate the herbicidal mechanism of cyanazine.

In vivo activity of cyanazine is demonstrated in agricultural settings where it effectively controls annual grasses and broadleaf weeds. The herbicide is applied pre- or post-emergence to target crops. Its systemic activity allows it to be absorbed through roots and foliage, translocating throughout the plant to achieve effective weed control. The compound's selectivity is based on differential metabolism in crops versus weeds.

Non-cellular assays for cyanazine typically involve measuring its herbicidal activity in biochemical systems. Photosystem II inhibition is assessed using isolated thylakoid membranes or chloroplasts, measuring the reduction of electron transport or fluorescence quenching. Binding assays with the D1 protein can determine the compound's affinity for its target site. These cell-free systems allow for characterization of the compound's mechanism of action.

Cellular assays for cyanazine are conducted using plant cell cultures or algal species to assess herbicidal activity. Cells are treated with varying concentrations of the herbicide, and photosynthetic activity is measured by oxygen evolution or chlorophyll fluorescence. Cell growth and viability are assessed to determine the compound's phytotoxicity. These assays are used to screen for herbicidal activity and to study resistance mechanisms.

In vivo animal experiments for cyanazine are typically conducted in toxicology studies to assess its safety profile. The compound is administered to rodents via oral gavage, and various endpoints are assessed including organ toxicity, developmental effects, and carcinogenicity. Cyanazine has been listed as a developmental toxicant. These studies are used to establish safe exposure limits for agricultural workers and consumers.

Absorption, Distribution and Excretion
Cyazine is rapidly metabolized in rats and dogs and excreted within 4 days. Studies have shown that after oral administration of 14C cyanazine, the substance is rapidly absorbed and metabolized; approximately 40% of the administered dose is excreted in the urine and 47% in the feces. In rats and dogs, cyanazine is rapidly metabolized after oral administration and excreted within approximately 4 days. Metabolism/Metabolites The main metabolic pathway of cyanazine in rats is N-deethylation to form an amine. Additionally, N-acetylcysteine derivatives were detected in the urine. Dechlorination to form 2-hydroxytriazine and cyano hydrolysis to form an amide, followed by further hydrolysis to form a carboxyl analog, were also observed. The 2-hydroxy compound is the main metabolite in the feces. Glutathione conjugates are present in the bile. Red amaranth does not hydroxylate cyanazine but binds to this compound. Hydrolysis, N-dealkylation, and glutathione conjugates were observed in corn. Hydroxy acids and dealkylated hydroxy acids were observed in maize. The carboxyl group on the isopropyl amino side chain inhibited the dealkylation of the ethylamino group. Five days after foliar spraying with 14C cyanazine, water-soluble and chloroform-soluble metabolites were found in millet and foxtail millet. The nitrile group was hydrolyzed, and the triazine ring was hydroxylated at the 2-position. The degradation of cyanazine proceeds first via hydrolysis of the nitrile group, followed by a slower hydrolysis of the 2-chloro group. 2-Hydroxycyanazine was the major metabolite found in rat feces. Rats also produced 4-amino and N-acetylcysteine derivatives and hydrolyzed the cyanide group to the corresponding amide and carboxyl derivatives. Organic nitriles are converted to cyanide ions in the liver by cytochrome P450 enzymes. Cyanide is rapidly absorbed and distributed throughout the body. Cyanide is primarily metabolized to thiocyanate by thiocyanate esterase or 3-mercaptopyruvate thiotransferase. Cyanide metabolites are excreted in the urine. (L96)

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Pharmacokinetic properties of cyanazine have been studied in toxicological contexts. The compound has a vapor pressure of 1.6 × 10-9 mmHg at 20°C and a solubility in water of 171 mg/L at 25°C. It is soluble in organic solvents including benzene, chloroform, and ethanol. The compound is absorbed through ingestion and inhalation, distributed throughout the body, and metabolized and excreted in urine and feces.

Toxicity Summary
Organic nitriles can decompose into cyanide ions both in vivo and in vitro. Therefore, the main toxic mechanism of organic nitriles is the production of toxic cyanide ions, or hydrogen cyanide. Cyanide ions are inhibitors of cytochrome c oxidase in the fourth electron transport chain complex (located on the mitochondrial membrane of eukaryotic cells). It forms a complex with the ferric atom in this enzyme. The binding of cyanide ions to this cytochrome prevents electrons from being transferred from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted, and the cell can no longer perform aerobic respiration to produce ATP for energy. Tissues that rely primarily on aerobic respiration, such as the central nervous system and the heart, are particularly susceptible to this. Cyanide can also exert some toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydrocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinate dehydrogenase, and copper/zinc superoxide dismutase. Cyanide binds to the iron ions in methemoglobin to form inactive methemoglobin cyanide. (L97)

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Toxicity Data
LCLo (Rat)> 4,900 mg/m3

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Non-human Toxicity Values
Oral LD50 in rats: 288 mg/kg
Dermal LD50 in rabbits: <2000 mg/kg
Oral LD50 in mice: 380 mg/kg
Dermal LD50 in rats: >1200 mg/kg
For more complete non-human toxicity data for cyanazines (out of 16), please visit the HSDB record page.

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Toxicological data for cyanazine indicate that it is a developmental toxicant. The compound has been evaluated by the EPA and other regulatory agencies. Maternal toxicity may contribute to the developmental effects observed. The compound is listed as a potential carcinogen. Occupational exposure limits have been established to protect agricultural workers. The compound should be handled with appropriate personal protective equipment.

[1]. Preparation and characterization of cyanazine–ydroxypropyl-beta-cyclodextrin inclusion complex. RSC Advances, 2019. 9(45), 26109–26115.

Depending on state or federal labeling requirements, cyanazine may be developmentally toxic. Cyanazine is a colorless crystalline powder, non-corrosive when dry, and is used as a selective systemic herbicide. Cyanazine is a chloro-1,3,5-triazine, formed by substituting 2-chloro-1,3,5-triazine at positions 6 and 4 with ethylamino and (2-cyanopropyl-2-yl)amino groups, respectively. It is both a herbicide and an environmental pollutant and exogenous substance. It is a 1,3,5-triazinylaminonitrile, and also a chloro-1,3,5-triazine. Cyanazine is marketed by DuPont Chemicals under the trade name Bladex and has been used since 1971. In the 1990s, it was the fourth most commonly used synthetic chemical pesticide in US agriculture. Cyanazine is a triazine herbicide used as a pre- and post-emergence herbicide to control annual grasses and broadleaf weeds. It is primarily used on corn, with smaller amounts on cotton, and less than 1% on sorghum and fallow wheat. Due to its teratogenicity and its presence in groundwater, cyanazine is listed as a restricted-use pesticide (RUP) by the U.S. Environmental Protection Agency (EPA). Cyanazine can cause various birth defects in animals over a wide dose range. A long-term study of rats fed cyanazine showed that moderate doses resulted in increased brain weight and decreased kidney weight in third-generation offspring.

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Mechanism of Action
Photosynthesis inhibitor.

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Other information includes cyanazine's use as a selective systemic herbicide for pre- and post-emergent control of annual grasses and broadleaf weeds. It is widely used in corn, soybean, and sorghum production. The compound is a member of the triazine family of herbicides. It is available in various formulations including wettable powders and liquid concentrates. Regulatory restrictions may apply to its use in certain regions.

C9H13CLN6

240.69

240.089

21725-46-2

Cyanazine-d5;1190003-29-2

30773

White to off-white solid powder

1.3±0.1 g/cm3

349.9±44.0 °C at 760 mmHg

167.5-169 °C ; 168 °C

165.4±28.4 °C

0.0±0.8 mmHg at 25°C

1.614

0.2

2

6

4

16

272

0

CCNC1=NC(=NC(=N1)Cl)NC(C)(C)C#N

MZZBPDKVEFVLFF-UHFFFAOYSA-N

InChI=1S/C9H13ClN6/c1-4-12-7-13-6(10)14-8(15-7)16-9(2,3)5-11/h4H2,1-3H3,(H2,12,13,14,15,16)

2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl]amino]-2-methylpropanenitrile

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product requires protection from light (avoid light exposure) during transportation and storage.

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 (415.47 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (10.39 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 (10.39 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.)