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Send EmailCysteine, L-Cysteine, E920, 52-90-4
L-Cysteine / (2R)-2-Amino-3-sulfanylpropanoic Acid / Cysteine
CAS Number: 52-90-4
EC Number: 200-158-2
| Parameter | Detail |
|---|---|
| Product Name | L-Cysteine |
| CAS Number | 52-90-4 |
| EC Number (EINECS) | 200-158-2 |
| Molecular Formula | C₃H₇NO₂S |
| Molecular Weight | 121.16 g/mol |
| E Number | E920 |
| IUPAC Name | (2R)-2-Amino-3-sulfanylpropanoic acid |
| Other Names | L-Cysteine, Cysteine, (R)-2-Amino-3-mercaptopropionic acid, L-2-Amino-3-mercaptopropionic acid |
| Appearance | White crystalline powder |
| Odor | Slight sulfurous odor |
L-Cysteine is a sulfur-containing, non-essential amino acid that is naturally found in proteins. It is one of the 20 standard amino acids and contains a thiol (-SH) group, which gives it unique antioxidant properties. L-Cysteine plays a critical role in protein synthesis, detoxification, and the formation of glutathione, one of the body's most important antioxidants. It is widely used in the food industry as a dough conditioner (E920), in the pharmaceutical industry, in cosmetics, and in biochemical research. L-Cysteine is optically active and exists in both L- and D-forms; the L-form is the naturally occurring and biologically active enantiomer.
| Type | Name |
|---|---|
| Common Names | L-Cysteine, Cysteine, L-2-Amino-3-mercaptopropionic acid |
| Chemical Names | (2R)-2-Amino-3-sulfanylpropanoic acid, (R)-2-Amino-3-mercaptopropionic acid |
| Abbreviations | Cys, C, L-Cys |
| E Number | E920 |
| CAS Number | 52-90-4 |
| EC Number | 200-158-2 |
| UN Number | Not applicable (not classified as dangerous goods) |
| HS Code | 2930.90 |
L-Cysteine is a sulfur-containing amino acid with a thiol (-SH) functional group. The structure consists of an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a thiol-containing side chain (-CH₂-SH) attached to a central chiral carbon atom.
Structural Formula:
H
|
HOOC - C - NH₂
|
CH₂
|
SH
Simplified Representation:
H
|
HOOC - C - NH₂
|
CH₂ - SH
C₃H₇NO₂S
121.16 g/mol
| Feature | Description |
|---|---|
| Functional Groups | Amino group (-NH₂), Carboxyl group (-COOH), Thiol group (-SH) |
| Chiral Center | Central carbon atom (C2) is chiral; L-configuration |
| Sulfur Content | Contains one sulfur atom per molecule |
| Isoelectric Point (pI) | 5.02 |
| pKa Values | pKa1 (COOH) = 1.71; pKa2 (NH₃⁺) = 8.33; pKa3 (SH) = 10.78 |
| Optical Rotation | [α]²⁰D = +6.5° to +8.5° (c=10, 1N HCl) |
| Property | Value |
|---|---|
| Appearance | White crystalline powder |
| Odor | Slight sulfurous odor |
| Molecular Weight | 121.16 g/mol |
| Melting Point | ~240°C (decomposes) |
| Solubility in Water | Soluble (~25 mg/mL at 20°C) |
| Solubility in Ethanol | Slightly soluble |
| Solubility in Ether | Insoluble |
| pH (1% aqueous solution) | 4.5 – 5.5 |
| Density | ~1.5 g/cm³ |
| Optical Rotation | [α]²⁰D = +6.5° to +8.5° (c=10, 1N HCl) |
| Isoelectric Point (pI) | 5.02 |
| pKa1 (COOH) | 1.71 |
| pKa2 (NH₃⁺) | 8.33 |
| pKa3 (SH) | 10.78 |
| Stability | Stable under proper storage conditions; sensitive to moisture and oxidation |
| Hygroscopicity | Slightly hygroscopic |
| Solvent | Solubility | Conditions |
|---|---|---|
| Water | ~25 mg/mL | 20°C |
| Water | Higher solubility | 50°C |
| Ethanol | Slightly soluble | 25°C |
| Methanol | Slightly soluble | 25°C |
| Ether | Insoluble | 25°C |
| Acetone | Insoluble | 25°C |
| Chloroform | Insoluble | 25°C |
| Dilute HCl | Soluble | 25°C |
| Dilute NaOH | Soluble | 25°C |
| Property | Description |
|---|---|
| Chemical Character | Amphoteric (both acidic and basic properties) |
| Thiol Group | The -SH group is highly reactive; undergoes oxidation to form disulfides (cystine) |
| Oxidation | 2 L-Cysteine → L-Cystine (disulfide bond formation) |
| Reduction | L-Cystine → 2 L-Cysteine (disulfide bond cleavage) |
| pH Behavior | Cationic at low pH, zwitterionic at neutral pH, anionic at high pH |
| Chelation | Can form complexes with metal ions (e.g., Cu²⁺, Zn²⁺, Fe²⁺) |
| Incompatible Materials | Strong oxidizers, strong bases, heavy metal ions |
2 L-Cysteine + [O] → L-Cystine + H₂O
L-Cystine + 2[H] → 2 L-Cysteine
2 L-Cysteine + Cu²⁺ → Cu(Cys)₂ + 2H⁺
Cationic form (pH < pI): H₃N⁺-CH(COOH)-CH₂-SH
Zwitterionic form (pH = pI): H₃N⁺-CH(COO⁻)-CH₂-SH
Anionic form (pH > pI): H₂N-CH(COO⁻)-CH₂-SH
L-Cysteine is produced by several methods:
| Stage | Process | Description |
|---|---|---|
| 1 | Raw Material | Keratin-rich sources (human hair, animal hair, feathers) are used as raw material. |
| 2 | Hydrolysis | Keratin is hydrolyzed with hydrochloric acid (HCl) at high temperature. |
| 3 | Neutralization | The hydrolysate is neutralized with sodium hydroxide (NaOH). |
| 4 | Crystallization | L-Cysteine is crystallized from the solution. |
| 5 | Purification | The crystals are purified by recrystallization. |
| 6 | Drying | The purified product is dried to obtain final L-Cysteine powder. |
| Stage | Process | Description |
|---|---|---|
| 1 | Fermentation | Microorganisms (e.g., E. coli) are cultured in fermentation tanks containing sugar and nutrient media. |
| 2 | Biosynthesis | L-Cysteine is biosynthesized by the microorganisms. |
| 3 | Separation | L-Cysteine is separated from the fermentation broth. |
| 4 | Purification | The product is purified to high purity. |
| 5 | Drying | The purified product is dried to obtain final L-Cysteine powder. |
| Property | Description |
|---|---|
| Biological Role | Proteinogenic amino acid; component of proteins and peptides |
| Metabolic Role | Precursor for glutathione, taurine, and coenzyme A |
| Antioxidant Activity | Direct scavenger of free radicals; precursor to glutathione (GSH) |
| Detoxification | Binds to toxic heavy metals and metabolites for excretion |
| Protein Structure | Forms disulfide bonds that stabilize protein tertiary structure |
| Essentiality | Conditionally essential (non-essential in healthy individuals, essential under certain conditions) |
| Application | Description |
|---|---|
| Dough Conditioner | Improves dough elasticity and extensibility in bread and bakery products. |
| Flavor Enhancer | Used as a flavoring agent in some processed foods. |
| Anti-staling Agent | Extends the shelf life of bakery products by preventing staling. |
| Antioxidant | Prevents oxidative degradation of food products. |
| Application | Description |
|---|---|
| Antioxidant Supplement | Used in dietary supplements for its antioxidant properties. |
| Cell Culture Media | Essential component of cell culture media for in vitro studies. |
| Pharmaceutical Intermediate | Used in the synthesis of various pharmaceutical compounds. |
| Detoxification Aid | Supports liver function and detoxification processes. |
| Wound Healing | Used in wound healing formulations. |
| Application | Description |
|---|---|
| Hair Care | Promotes keratin synthesis; used in hair growth and strengthening products. |
| Skin Care | Antioxidant properties; used in anti-aging and skin-brightening formulations. |
| Nail Care | Supports nail health and strength. |
| Application | Description |
|---|---|
| Protein Studies | Used in protein structure and function studies (disulfide bond analysis). |
| Enzyme Studies | Used as a substrate or inhibitor in enzyme assays. |
| Cell Culture | Component of defined cell culture media. |
| Antioxidant Studies | Used as a standard in antioxidant activity assays. |
| Application | Description |
|---|---|
| Animal Nutrition | Used as a feed additive to improve growth and health. |
| Fragrance Industry | Used in the synthesis of flavor and fragrance compounds. |
| Photographic Industry | Used in photographic developers. |
| Property | L-Cysteine | L-Cystine |
|---|---|---|
| Structure | Monomeric (one amino acid molecule) | Dimeric (two cysteine molecules linked by disulfide bond) |
| Functional Group | Thiol (-SH) | Disulfide (-S-S-) |
| Oxidation State | Reduced | Oxidized |
| Solubility | Soluble in water | Less soluble in water |
| Stability | Sensitive to oxidation | More stable |
| Interconversion | 2 Cysteine ⇌ 1 Cystine |
| Substance / Environment | Compatibility | Description |
|---|---|---|
| Water | COMPATIBLE | Soluble; stable in aqueous solution at pH 2-6. |
| Acids (HCl, H₂SO₄) | COMPATIBLE | Soluble in dilute acids; stable. |
| Alkalis (NaOH, KOH) | COMPATIBLE | Soluble in dilute alkalis; may oxidize in strong alkali. |
| Oxidizers | INCOMPATIBLE | Oxidation to cystine; may cause degradation. |
| Reducing Agents | COMPATIBLE | Stable; may enhance reduction. |
| Heavy Metal Ions | LIMITED | Chelation may occur; may cause discoloration. |
| Air / Oxygen | LIMITED | Slow oxidation to cystine; store under inert atmosphere. |
| Light | COMPATIBLE | Stable; protect from UV light for long-term storage. |
| Moisture | LIMITED | Slightly hygroscopic; protect from moisture. |
| Parameter | Value |
|---|---|
| Acute Oral Toxicity (LD50, Rat) | > 3000 mg/kg (low toxicity) |
| Acute Dermal Toxicity (LD50, Rabbit) | > 2000 mg/kg |
| Acute Inhalation Toxicity | Low risk; may cause mild respiratory irritation. |
| Skin Irritation | Mild irritant in powder form. |
| Eye Irritation | May cause mild eye irritation. |
| Skin Sensitization | Not classified as a sensitizer. |
| Mutagenicity | Negative. |
| Carcinogenicity | Not classified as a carcinogen. |
| Reproductive Toxicity | Not classified as a reproductive toxin. |
| Target Organs | No specific target organs identified. |
| High Dose Effects | May cause gastrointestinal discomfort (nausea, vomiting, diarrhea). |
GHS Classification (Generally Not Classified as Hazardous):
| Hazard Class | Category | H-Statement |
|---|---|---|
| Not classified as hazardous | - | - |
Signal Word: None (not classified as hazardous)
Hazard Pictograms: None (not classified as hazardous)
Hazard Statements (H-Codes): None (not classified as hazardous)
Safety Phrases (Historically):
| Code | Statement |
|---|---|
| S22 | Do not breathe dust. |
| S24/25 | Avoid contact with skin and eyes. |
| S36/37/39 | Wear suitable protective clothing, gloves, and eye/face protection. |
| Code | Statement |
|---|---|
| P261 | Avoid breathing dust/fume/gas/mist/vapors/spray. |
| P264 | Wash hands thoroughly after handling. |
| P280 | Wear protective gloves/protective clothing/eye protection/face protection. |
| P305+P351+P338 | IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses if present. |
| P337+P313 | If eye irritation persists: Get medical advice/attention. |
| P501 | Dispose of contents/container in accordance with local regulations. |
| Route of Exposure | Action to Be Taken |
|---|---|
| Inhalation | Move to fresh air. If respiratory irritation persists, seek medical attention. |
| Skin Contact | Wash with plenty of soap and water. Remove contaminated clothing. If irritation persists, consult a physician. |
| Eye Contact | Rinse thoroughly with plenty of water for at least 15 minutes. Remove contact lenses. If irritation persists, seek medical attention. |
| Ingestion | Rinse mouth with water. Drink plenty of water. Do not induce vomiting. If large amount is swallowed, seek medical attention. |
| General Note | If symptoms persist, always consult a healthcare facility. |
| Parameter | Information |
|---|---|
| Fire Hazard | Not flammable; may decompose at high temperatures. |
| Hazards During Fire | Thermal decomposition produces toxic fumes including sulfur oxides (SOₓ), carbon monoxide, carbon dioxide, and nitrogen oxides. |
| Suitable Extinguishing Media | Water spray, CO₂, dry chemical powder, alcohol-resistant foam. |
| Special Protective Equipment | Self-contained breathing apparatus (SCBA), full protective clothing. |
| Special Precautions | Prevent fire-fighting water from entering the environment. |
| Parameter | Information |
|---|---|
| Personal Protection | Dust mask, protective goggles, gloves, coverall. |
| Ventilation | Increase ventilation; use local exhaust in confined spaces. |
| Containment | Cover spilled area to prevent dust dispersion. |
| Cleaning Methods | Collect dry using vacuum or careful sweeping. Avoid washing with water (product is soluble and may spread). |
| Environmental Precautions | Prevent entry into drains, sewers, and water bodies. |
| Waste Disposal | Dispose of in accordance with local regulations. |
| Parameter | Information |
|---|---|
| Storage Conditions | Store in a cool, dry, and well-ventilated area at room temperature (15-25°C). |
| Container Requirements | Keep tightly closed in original packaging. Protect from light and moisture. |
| Materials to Avoid | Strong oxidizers, strong bases, heavy metal ions, moisture, air (oxygen). |
| Shelf Life | 24 months (under proper storage conditions). |
| Stability Note | Slightly hygroscopic; sensitive to oxidation. Store under inert atmosphere (nitrogen) for long-term storage. |
| Packaging Options | 1 kg, 5 kg, 10 kg, 25 kg bags or drums. |
| Packaging Type | Quantity | Material |
|---|---|---|
| Polyethylene bag + outer bag | 1 – 5 kg | PE / Paper |
| Fiber drum | 10 – 25 kg | Cardboard / Plastic |
| Plastic drum | 25 kg | HDPE |
| Big-Bag | 500 – 1000 kg | Polypropylene |
| Parameter | Information |
|---|---|
| UN Number | Not applicable (not classified as dangerous goods). |
| Hazard Class | Not classified as hazardous for transport. |
| Packing Group | Not applicable. |
| ADR/RID | Not classified as dangerous goods. |
| IMDG Code | Not classified as dangerous goods. |
| IATA (Air) | Not classified as dangerous goods. |
| Marine Pollutant | No. |
| Transport Temperature | Ambient temperature; protect from moisture. |
| Region / Authority | Status |
|---|---|
| European Union | Approved as food additive E920. |
| USA (FDA) | Approved as food additive (GRAS - Generally Recognized as Safe). |
| Turkey | Approved as food additive; regulated by Turkish Food Codex. |
| Halal Certification | Available on request (depending on production method). |
| Kosher Certification | Available on request (depending on production method). |
| Pharmaceutical | Used as pharmaceutical intermediate and excipient. |
| Cosmetics | Permitted in cosmetic formulations. |
| Sector | Suitability | Description |
|---|---|---|
| Food Industry | HIGH | Dough conditioner (E920), antioxidant, flavor enhancer. |
| Pharmaceuticals | HIGH | Cell culture media, antioxidant, detoxification aid. |
| Cosmetics | HIGH | Hair and skin care products, anti-aging formulations. |
| Biochemical Research | HIGH | Protein studies, enzyme assays, cell culture. |
| Animal Nutrition | MODERATE | Feed additive. |
| Fragrance / Flavor | MODERATE | Synthesis of flavor and fragrance compounds. |
| Property | Value |
|---|---|
| CAS Number | 52-90-4 |
| EC Number | 200-158-2 |
| Molecular Formula | C₃H₇NO₂S |
| Molecular Weight | 121.16 g/mol |
| E Number | E920 |
| Appearance | White crystalline powder |
| Odor | Slight sulfurous |
| Melting Point | ~240°C (decomposes) |
| pH (1% solution) | 4.5 – 5.5 |
| Solubility in Water | ~25 mg/mL (20°C) |
| pI (Isoelectric Point) | 5.02 |
| Optical Rotation | +6.5° to +8.5° |
| Main Uses | Dough conditioner, antioxidant, cell culture, cosmetics |
| Shelf Life | 24 months |
| UN Number | Not applicable |
CRITICAL NOTICES:
Thiol Group Reactivity: The thiol (-SH) group in L-Cysteine is highly reactive and sensitive to oxidation. Exposure to air, oxygen, and light may cause oxidation to cystine. Store under inert atmosphere (nitrogen) for long-term storage.
pH Sensitivity: L-Cysteine is stable in acidic solutions (pH 2-6). At alkaline pH, oxidation is accelerated. Prepare solutions at pH 4.5-5.5 for optimal stability.
Heavy Metal Contamination: L-Cysteine can chelate heavy metal ions, which may cause discoloration or degradation. Use of high-purity materials is recommended for pharmaceutical and research applications.
Food Additive Regulations: E920 is approved in many countries but may have restrictions in organic food products. Check local regulations before use.
Production Source: L-Cysteine is traditionally produced from keratin (human hair, animal hair, feathers). Some consumers may have concerns about this source. Microbial fermentation products (vegetarian/vegan source) are available on request.
Allergen Status: L-Cysteine is generally considered non-allergenic. However, raw material sourcing may affect allergen status; verify with supplier.
GRAS Status: L-Cysteine is recognized as GRAS (Generally Recognized as Safe) by the FDA for its intended uses.
BEST PRACTICE RECOMMENDATIONS:
Storage: Store in a cool, dry, and well-ventilated area at room temperature. Keep containers tightly closed. Protect from light and moisture.
Personnel Protection: Use protective gloves, goggles, and dust mask. Ensure adequate ventilation.
Solution Preparation: Prepare solutions in deoxygenated water if possible. For long-term storage of solutions, add stabilizers such as EDTA or reduce pH.
Dosage Control: In food applications, follow recommended dosage guidelines. Overdosing may affect product quality.
Quality Assurance: Verify product source (traditional vs. microbial fermentation) and certifications (Halal, Kosher) as required.
Waste Management: Dispose of waste in accordance with local regulations.
LEGAL DISCLAIMER:
The information provided in this document is based on our current knowledge and experience and is presented in good faith; however, as all conditions of use are beyond our control, it does not constitute a binding specification or warranty. This Technical Data Sheet is for informational purposes only. Users are obligated to test the suitability of the product for their own applications. For complete safety, storage, handling, transport, waste, and regulatory compliance information, the official Safety Data Sheet (SDS/MSDS) provided by the manufacturer/supplier must be consulted.