Toxicity Summary
IDENTIFICATION AND USE: Cysteine forms white or colorless crystals. It is used in biochemical and nutrition research, as a reducing agent in bread doughs (up to 90 ppm). It is also used as flavor enhancer and medication, including veterinary medication. HUMAN EXPOSURE AND TOXICITY: Cysteine solution (3%) was not irritating for human eyes. ANIMAL STUDIES: A single ocular application of L-cysteine to rabbits at a dose of 0.1 g produced slight irritant effects, which were fully reversible within 48 hours. The single dermal application of L-cysteine to three rabbits at a dose of 0.5 g showed neither irritant nor corrosive effects. Decreased litter size observed in rats receiving high-dose cysteine, which was related to the degeneration and/or death of ovulated unfertilized oocytes and embryos with changes in the zona pellucida, which was already affected in the ovary. Pregnant mice and rats were treated s.c. with 1.2 mg per g on the last day of pregnancy and brain degeneration was observed one day later in the fetus. L-Cysteine is considered to be non-mutagenic in the HPRT locus using V79 cells of the Chinese Hamster. L-Cysteine did not induce structural chromosomal aberrations in the V79 Chinese hamster cell line. ECOTOXICITY STUDIES: The objective of the study was to determine the effects of cysteine on postthaw sperm motility, duration of sperm motility, DNA damage, and fertility in the common carp (Cyprinus carpio). Supplementation with cysteine increased the fertilization and hatching rate and decreased DNA damage.

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Non-Human Toxicity Values
LD50 Rat dermal >2000 mg/kg body weight
LD50 Rat oral 1890 mg/kg
LD50 Rat ip 1620 mg/kg
LD50 Rat sc 1550 mg/kg
For more Non-Human Toxicity Values (Complete) data for CYSTEINE (7 total), please visit the HSDB record page.

[1]. Impact of Deuterium Substitution on the Pharmacokinetics of Pharmaceuticals. Ann Pharmacother. 2019;53(2):211-216.

[2]. L-cysteine suppresses ghrelin and reduces appetite in rodents and humans. Int J Obes (Lond). 2015 Mar;39(3):447-55.

Cysteine is a sulfur-containing amino acid that is propanoic acid with an amino group at position 2 and a sulfanyl group at position 3. It has a role as a fundamental metabolite. It is an alpha-amino acid, a polar amino acid and a sulfur-containing amino acid. It contains a sulfanylmethyl group. It is a conjugate base of a cysteinium. It is a conjugate acid of a cysteinate(1-). It is a tautomer of a cysteine zwitterion.
DL-Cysteine has been reported in Drosophila melanogaster, Trifolium repens, and other organisms with data available.
See also: Cysteine (annotation moved to).

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Therapeutic Uses
/EXPL THER/ Acetaminophen-cysteine adducts (APAP-CYS) are a serum biomarker of acetaminophen exposure, formed when the oxidative metabolite of acetaminophen binds to cysteine residues of hepatic proteins. APAP-CYS adducts become elevated in cases of acute liver failure following acetaminophen overdose and have been proposed as a diagnostic tool to identify acetaminophen-induced acute liver failure when standard testing is inconclusive.
/EXPL THER/ Lead is a toxic heavy metal that adversely affects nervous tissues; it often occurs as an environmental pollutant. We investigated histological changes in the cerebral cortex, hippocampus and cerebellum of adult albino mice following exposure to lead acetate. We also studied the possible ameliorative effect of the chelating agent, L-cysteine, on lead-induced neurotoxicity. We divided albino mice into six groups: 1) vehicle-only control, 2) L-cysteine control, 3 and 4) treated for 7 days with 20 and 40 mg/kg lead acetate, respectively, and 5 and 6) treated for 7 days with 20 and 40 mg/kg lead acetate, respectively, followed by 50 mg/kg L-cysteine for 7 days. Lead acetate administration caused disorganization of cell layers, neuronal loss and degeneration, and neuropil vacuolization. Brain sections from lead-intoxicated mice treated with L-cysteine showed fewer pathological changes; the neuropil showed less vacuolization and the neurons appeared less damaged. L-cysteine at the dose we used only marginally alleviated lead-induced toxicity.
/EXPL THER/ In hamster lung cell cultures addn of l-Cysteine or vit C to media protects against or reverses abnormal growth & malignant transformation in aged controls (1-2 yr old) or young (3-6 mo) after repeated exposure to smoke of tobacco or marijuana cigarettes.
/EXPL THER/ L-Cysteine admin orally or ip to rats protected against acute toxicity of methylmercury chloride, reducing mercury content in kidney & brain but not in liver.
For more Therapeutic Uses (Complete) data for CYSTEINE (7 total), please visit the HSDB record page.

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Pharmacodynamics
Due to this ability to undergo redox reactions, cysteine has antioxidant properties. Cysteine is an important source of sulfur in human metabolism, and although it is classified as a non-essential amino acid, cysteine may be essential for infants, the elderly, and individuals with certain metabolic disease or who suffer from malabsorption syndromes. Cysteine may at some point be recognized as an essential or conditionally essential amino acid.

C3H715NO2S

122.15

122.016

204523-09-1

L-Cysteine;52-90-4

594

White to off-white solid powder

1.3±0.1 g/cm3

220 °C (dec.)(lit.)

1.550

0.028

3

4

2

7

75.3

0

XUJNEKJLAYXESH-UHFFFAOYSA-N

InChI=1S/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)

2-amino-3-sulfanylpropanoic acid

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light.

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.)