Herbicidal agent

The commercial herbicide formulation Betanal® Expert and its active ingredients (a.i.s) ethofumesate, phenmedipham and desmedipham were focused in this study. Following questions yielding from a previous study, an in-depth analysis of the reproductive toxicity of the pesticide was made. Long-term exposures of Daphnia magna and Daphnia longispina to Betanal® Expert, to each a.i. and to a customised mixture matching the a.i.s ratio within the commercial formulation were carried out, and deleterious effects in the offspring were recorded. This intended to clarify whether (1) the tested compounds induce reproductive injury; (2) there is interspecific variation in daphnids tolerance to the compounds; (3) there is an interaction between chemicals in combined treatments; and (4) the so-called inert ingredients added to the commercial formulation contribute to the toxicity of the herbicide. Generally, developmental impair was observed in both species (egg abortion and release of undeveloped embryos or dead offspring) at concentrations of any of the a.i.s below 1 mg L(-1). Ethofumesate was invariably the least toxic pesticide, and D. magna tended to be of slightly higher sensitivity to the exposures compared to D. longispina. Joint exposures indicated that the a.i.s can interact, inducing more than and less than additive effects for Betanal® Expert and the customised a.i. mixture, respectively. This indicates that inert ingredients co-formulating the commercial pesticide (which are absent from the customised a.i. mixture) actually contribute to its overall toxicity. This study constitutes an add-on to the discussion on the ecotoxicological framework required for authorisation of pesticide trade and usage. The results support the need to consider test species, long-term hazardous potential and toxicity of commercial formulations rather than solely that of active ingredients, as relevant variables in pesticide regulation[1].

Absorption, Distribution and Excretion
In rats, dogs & humans ... phenmedipham ... /is/ readily absorbed ... .
RECOVERY OF /ORALLY/ ADMIN DOSE /TO RATS/ IN URINE & FECES, AT 72 HR AFTER TREATMENT, WAS ... 99% ... URINE ... PRIMARY ROUTE OF ELIMINATION, WITH 80% ... EXCRETED VIA URINE IN INITIAL 24 HR ... TRACE AMT OF RADIOLABEL ... IN KIDNEY ... 0.039 PPM ... ALL OTHER TISSUES FELL BELOW THIS LEVEL.
It is absorbed through leaves & has little action by way of soil & roots.

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Metabolism / Metabolites
WHEN ADMIN TO WHITE RATS, PHENMEDIPHAM ... RAPIDLY METABOLIZED ... HYDROLYSIS YIELDED METHYL N-(3-HYDROXYPHENOL) CARBAMATE (MHPC) ... HYDROXYPHENYLCARBAMATES FORMED ... DEGRADED TO M-AMINOPHENOL WHICH WAS ACETYLATED TO ... 3-HYDROXYACETANILIDE. THESE METABOLITES WERE THEN CONJUGATED AS GLUCURONIDES & SULFATES.
BETANAL ... WAS RAPIDLY METABOLIZED BY RATS TO CORRESPONDING PHENOL ... (60-70%)(WHICH WAS PARTLY CONJUGATED) & M-HYDROXYANILINE, WHICH WAS EXCRETED AS M-HYDROXYACETANILIDE ... (2%).
The carbamates are hydrolyzed enzymatically by the liver; degradation products are excreted by the kidneys and the liver. (L793)

Toxicity Summary
Phenmedipham is a cholinesterase or acetylcholinesterase (AChE) inhibitor. Carbamates form unstable complexes with chlolinesterases by carbamoylation of the active sites of the enzymes. This inhibition is reversible. A cholinesterase inhibitor suppresses the action of acetylcholine esterase. Because of its essential function, chemicals that interfere with the action of acetylcholine esterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses. Headache, salivation, nausea, vomiting, abdominal pain and diarrhea are often prominent at higher levels of exposure. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop.

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Toxicity Summary
Phenmedipham is a cholinesterase or acetylcholinesterase (AChE) inhibitor. Carbamates form unstable complexes with chlolinesterases by carbamoylation of the active sites of the enzymes. This inhibition is reversible. A cholinesterase inhibitor suppresses the action of acetylcholine esterase. Because of its essential function, chemicals that interfere with the action of acetylcholine esterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses. Headache, salivation, nausea, vomiting, abdominal pain and diarrhea are often prominent at higher levels of exposure. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop.

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Toxicity Data
LD50: >8000 mg/kg (Rat, oral)

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Treatment
If the compound has been ingested, rapid gastric lavage should be performed using 5% sodium bicarbonate. For skin contact, the skin should be washed with soap and water. If the compound has entered the eyes, they should be washed with large quantities of isotonic saline or water. In serious cases, atropine and/or pralidoxime should be administered. Anti-cholinergic drugs work to counteract the effects of excess acetylcholine and reactivate AChE. Atropine can be used as an antidote in conjunction with pralidoxime or other pyridinium oximes (such as trimedoxime or obidoxime), though the use of '-oximes' has been found to be of no benefit, or possibly harmful, in at least two meta-analyses. Atropine is a muscarinic antagonist, and thus blocks the action of acetylcholine peripherally.

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Toxicity Data
LD50: >8000 mg/kg (Rat, oral)

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Non-Human Toxicity Values
LD50 Dog oral 4000 mg/kg
LD50 Guinea pig oral 4000 mg/kg
LD50 Chicken oral 3000 mg/kg
LD50 Rat percutaneous 4000 mg/kg
LD50 Rat oral >8000 mg/kg

[1]. Reproductive and Developmental Toxicity of the Herbicide Betanal® Expert and Corresponding Active Ingredients to Daphnia SPP. Environ Sci Pollut Res Int. 2016 Jul;23(13):13276-87.

Phenmedipham appears as colorless crystals or white powder. (NTP, 1992)
Phenmedipham is a carbamate ester that is (3-methylphenyl)carbamic acid in which the hydrogen of the hydroxy group has been replaced by a 3-[(methoxycarbonyl)amino]phenyl group. It has a role as an environmental contaminant, a xenobiotic and a herbicide.
Phenmedipham is a selective herbicide of the carbanilate and biscarbamate classes. Carbamate pesticides are derived from carbamic acid and kill insects in a similar fashion as organophosphate insecticides. They are widely used in homes, gardens and agriculture. The first carbamate, carbaryl, was introduced in 1956 and more of it has been used throughout the world than all other carbamates combined. Because of carbaryl's relatively low mammalian oral and dermal toxicity and broad control spectrum, it has had wide use in lawn and garden settings. Most of the carbamates are extremely toxic to Hymenoptera, and precautions must be taken to avoid exposure to foraging bees or parasitic wasps. Some of the carbamates are translocated within plants, making them an effective systemic treatment. Phenmedipham was developed by Schering AG and approved for use in the United States in 1970. Today, about 100 tons of Phenmedipham are used each year. It is commonly used in beet, spinach, and strawberry crops to protect against weeds, often in comination with Desmedipham under the trade names Betanal or Betamax. (L795)

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Mechanism of Action
BETANAL EXERTS ITS HERBICIDAL ACTION BY DISRUPTING PHOTOCHEMICAL REACTIONS. MAJOR CHANGES INVOLVED PHOSPHORYLATION & ITS RELATED NONCYCLIC ELECTRON TRANSPORT.
PHENMEDIPHAM IS STRONG INHIBITOR OF HILL REACTION /IN PLANTS/.
At concn near 2X10-4 M, phenmedipham inhibited electron transfer in potato and mung bean mitochondria. The inhibition seemed to be localized in the flavoprotein region. It affected preferentially the exogenous nicotinamide-adenine dinucleotide (NADH) dehydrogenase, in potato mitochondria. Succinate dehydrogenase was less inhibited. Photosynthesis was completely inhibited by 2X10-7 M phenmedipham.

C16H16N2O4

300.31

300.11

C, 63.99; H, 5.37; N, 9.33; O, 21.31

13684-63-4

Phenmedipham-d3;1773497-41-8

24744

White to off-white solid powder

1.2±0.1 g/cm3

510.3±60.0 °C at 760 mmHg

140-144°C

262.4±32.9 °C

0.0±1.4 mmHg at 25°C

1.569

4.42

2

4

5

22

388

0

IDOWTHOLJBTAFI-UHFFFAOYSA-N

InChI=1S/C16H16N2O4/c1-11-5-3-6-12(9-11)18-16(20)22-14-8-4-7-13(10-14)17-15(19)21-2/h3-10H,1-2H3,(H,17,19)(H,18,20)

[3-(methoxycarbonylamino)phenyl] N-(3-methylphenyl)carbamate

HSDB 1402; Fenmedifam; Phenmedipham; 13684-63-4; 3-((Methoxycarbonyl)amino)phenyl m-tolylcarbamate; BETANAL; Fenmedifam; Spin-aid; Phenmediphame; Kemifam; Phenmedipham

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.)