CYSTEINE HYDROCHLORIDE

Cysteine hydrochloride is a sulfur-containing amino acid that plays a crucial role in protein structure and cellular metabolism, but it can be relatively unstable, therefore, converting it to cysteine hydrochloride helps preserve its properties and extend its shelf life.
Cysteine hydrochloride is a thiol-containing amino acid that is oxidized to form cystine. 
Cysteine hydrochloride is synthesized from methionine via the trans-sulfuration pathway in the adult, but newborn infants lack the enzyme, cystathionase, necessary to effect this conversion. 

CAS Number: 52-89-1
Molecular Formula: C3H8ClNO2S
Molecular Weight: 157.62
EINECS Number: 200-157-7

Synonyms: Cystein chloride, CYSTEINE HYDROCHLORIDE, Cysteine chlorhydrate, cysteine-hcl, Cysteine hydrochloride (anhydrous), 3-Mercaptoalanine hydrochloride, CCRIS 3613, Cysteine hydrochloride anhydrous, NSC 8746, EINECS 200-157-7, WR 348, UNII-A9U1687S1S, EK 2367, AI3-18781, A9U1687S1S, Cysteine (as hydrochloride), CYSTEINE HYDROCHLORIDE, ANHYDROUS, EC 200-157-7, ELCYS, NOURESS, NSC-755898, CYSTEINE HYDROCHLORIDE (II), CYSTEINE HYDROCHLORIDE ANHYDROUS (II), CYSTEINE HYDROCHLORIDE ANHYDROUS [II], CYSTEINE HYDROCHLORIDE (USP MONOGRAPH), CYSTEINE HYDROCHLORIDE MONOHYDRATE (EP IMPURITY), CYSTEINE HYDROCHLORIDE MONOHYDRATE (EP MONOGRAPH), 200-157-7, CYSTEINE HYDROCHLORIDE MONOHYDRATE, RefChem:56871, ZT934N0X4W, L-Cysteine hydrochloride, 52-89-1, L-Cysteine hydrochloride anhydrous, l-Cysteine.HCl, L-Cysteine, hydrochloride, l-cysteine hcl, L-CYSTEINE HCl anhydrous, (R)-Cysteine hydrochloride, L-(+)-Cysteine hydrochloride, Cysteine monohydrochloride, (R)-2-Amino-3-mercaptopropanoic acid hydrochloride, L-Cysteine monohydrochloride, Cysteine HCl (anhydrous), H-Cys-OH.HCl, Cysteine, L-, hydrochloride, MFCD00064553, L-Cysteine, hydrochloride (1:1), L-Cysteine (hydrochloride), DTXSID0020367, L-Cysteine hydrochloride, anhydrous, L-Cysteine hydrochloride hydrate, (2R)-2-amino-3-sulfanylpropanoic acid, hydrochloride, L-Cysteine, HCl, (2R)-2-amino-3-sulfanylpropanoic acid hydrochloride, Cysteine, L-, monohydrochloride, 345909-32-2 (.xH2O), cysteine-hydrochloride, L-cysteinium chloride, H-Cys-OH HCl, l-cysteine chlorhydrate, L-Cysteine hydro-chloride, SCHEMBL18161, DTXCID60367, L-Cysteinemethyl Hydrochloride, L-2-Amino-3-mercaptopropanoic acid monohydrochloride, MSK1405A, orb1299184, CHEMBL1200630, L-Cysteinƒe hydrochlorideanhydrous, CHEBI:91247, HY-Y0337A, Tox21_200699, s4815, AKOS015849225, CCG-266272, CS-W018517, CYSTEINE HYDROCHLORIDE [WHO-DD], FC38705, CAS-52-89-1, NCGƒC00258253-01, (2R)-2-amino-3-mercapto-propionic acid, AC-12796, AS-11682, L-CYSTEINE HYDROCHLORIDE [USP-RS], L-Cysteine hydrochloride, 98.0-102.0%, CYSTEINE HYDROCHLORIDE ANHYDROUS [MI], E72644, EN300-219524, (R)-2-Amino-3-mercaptopropanoicacidhydrochloride, (1R)-1-carboxy-2-sulfanylethan-1-aminium chloride, L-Cysteine hydrochloride, anhydrous, >=98% (TLC), (2R)-2-amino-3-sulfanyl-propanoic acid, hydrochloride, L-Cysteine hydrochloride, anhydrous, >=99.0% (RT), Q27163158, L-Cysteine hydrochloride, Vetec(TM) reagent grade, >=98%, (R)-Cysteine HCl,  (R)-1-carboxy-2-mercaptoethanaminium chloride,  L-(+)-Cysteine hydrochloride, L-Cysteine hydrochloride, anhydrous, from non-animal source, BioReagent, suitable for cell culture, >=98.0%, ƒL-(+)-α-amino-β-thiopropionic acid, L-β-mercapto, (2R)-2-Amino-3-sulfanylpropanoic acid hydrochloride, (2R)-2-Amino-3-mercaptopropanoic acid·hydrochloric acid, L-Cisteine·hydrochloride, L-Cysteine·hydrochloric acid, L-Cysteine hydrochlo, L-Cysteine hydrochloride anhydrous, extra pure

Cysteine hydrochloride is an amino acid. 
Cysteine hydrochloride is one of the main building block of proteins that are used in the body. 
When taken as a supplement, Cysteine hydrochloride is usually in the form of N-acetyl-L-cysteine (NAC). 

The body turns NAC into cysteine and then glutathione, a strong antioxidant. 
Cysteine hydrochloride has a wide range of uses. 
In the pharmaceutical industry it is used to improve hepatic function and pigmentation. 

In clinical nutrition Cysteine hydrochloride is used as an antioxidant agent. 
In the food industry Cysteine hydrochloride is used as an antioxidant for natural fruit juice products. 
Cysteine hydrochloride may also be used as an additive to amino acid injections to meet essential nutritional requirements in intravenous total parenteral nutrition.

Cysteine hydrochloride is a salt form of the amino acid cysteine, which has been combined with hydrochloric acid to improve its stability, solubility, and ease of use in medical and industrial applications. 
Therefore, Cysteine hydrochloride is generally considered to be an essential amino acid in infants.
A hydrochloride obtained by combining Cysteine hydrochloride with one molar equivalent of hydrogen chloride.

Cysteine hydrochloride symbol Cys or C) is a semiessentia proteinogenic amino acid with the formula HS−CH2−CH(NH2)−COOH. 
The thiol side chain in cysteine enables the formation of disulfide bonds, and often participates in enzymatic reactions as a nucleophile. 
Cysteine hydrochloride is chiral, but both D and L-cysteine are found in nature. 

Cysteine hydrochloride is a protein monomer in all biota, and D-cysteine acts as a signaling molecule in mammalian nervous systems.
Cysteine hydrochloride is named after its discovery in urine, which comes from the urinary bladder or cyst, from Greek κύστις kýstis, "bladder".
The thiol is susceptible to oxidation to give the disulfide derivative cystine, which serves an important structural role in many proteins. 

In this case, the symbol Cyx is sometimes used.
The deprotonated form can generally be described by the symbol Cym as well.
When used as a food additive, cysteine has the E number E920.

Cysteine hydrochloride is encoded by the codons UGU and UGC.
L-Cysteine hydrochloride hydrate is an orally active and essential amino acid, which acts as a precursor for biologically active molecules such as hydrogen sulphide (H2S), glutathione and taurine. 
Cysteine hydrochloride hydrate regulates CBS/H2S pathway, inhibits NF-κB activation and insulin and ghrelin secretion. 

Cysteine hydrochloride hydrochloride hydrate reduces blood sugar, vascular inflammation markers and appetite. 
Cysteine hydrochloride hydrate induces kidney damage. 
Cysteine hydrochloride hydrate can be used in the study of neurological diseases and diabetes.

Amino acid with a non-polar side chain. Sulfur containing side chains facilitate the formation of disulfide bonds in proteins. 
Cysteine hydrochloride is used as a reagent for reducing reactive sulfhydryl groups.
Cysteine hydrochloride is an amino acid commonly found as a component of total parenteral nutrition and used as an antidote for acetaminophen overdose.

Cysteine hydrochloride is a type of amino acid, which are the building blocks of proteins. 
The body makes Cysteine hydrochloride from another amino acid called methionine.
Cysteine hydrochloride is naturally found in foods, but because it's made in the body it doesn't need to be consumed in the diet. 

Cysteine hydrochloride has antioxidant effects and is used to make up antioxidants such as glutathione.
Cysteine hydrochloride Injection, USP, 50 mg/mL, is a sterile, nonpyrogenic solution. 
Cysteine hydrochloride USP,  Water for Injection, USP q.s.,  Air replaced with Nitrogen. 

Cysteine hydrochloride is a sulfur-containing amino acid. In premixed solutions of crystalline amino acids, cysteine is relatively unstable over time, eventually converting to insoluble cystine. 
To avoid such precipitation, L-Cysteine Hydrochloride Injection USP is intended to be used as an additive with Crystalline Amino Acid Injections immediately prior to administration to the patient.
Cysteine hydrochloride Injection, USP is intended for use only after dilution as an additive to Crystalline Amino Acid Injections to meet the intravenous amino acid nutritional requirements of infants receiving total parenteral nutrition.

Cysteine hydrochloride Pharma Grade is a white or almost white, crystalline powder or colourless crystals, that is freely soluble in water, and slightly soluble in alcohol. 
Cysteine hydrochloride is one of the 20 natural amino acids and, besides methionine, the only one which contains sulfur. This product is recommended for building blocks, formulations for pharmaceuticals and hair-perm formulations applications.

Melting point: 180°C
Alpha: 5.5 º (c=8, 6 N HCL)
Storage temp.: Inert atmosphere, Room Temperature
Solubility: H2O: 1 M at 20 °C, clear, colorless
Form: Solid
Color: White to light brown
Odor: odorless
Biological source: synthetic
Optical activity: [α]20/D +6.4±0.3°, c = 5% in 5 M HCl
Water Solubility: SOLUBLE
Sensitive: Hygroscopic
Merck: 14,2781
BRN: 3560277
Stability: Stable, but light, moisture and air sensitive. Incompatible with strong oxidizing agents, some metals.
InChIKey: IFQSXNOEEPCSLW-DKWTVANSSA-N
LogP: 0.235 (est)

Cysteine hydrochloride is a residue in high-protein foods. Some foods considered rich in cysteine include poultry, eggs, beef, and whole grains. 
In high-protein diets, cysteine may be partially responsible for reduced blood pressure and stroke risk.
Although classified as a nonessential amino acid, in rare cases, Cysteine hydrochloride may be essential for infants, the elderly, and individuals with certain metabolic diseases or who suffer from malabsorption syndromes. 

Cysteine hydrochloride can usually be synthesized by the human body under normal physiological conditions if a sufficient quantity of methionine is available.
Like other amino acids (not as a residue of a protein), cysteine exists as a zwitterion. 
Cysteine hydrochloride has l chirality in the older d/l notation based on homology to d- and l-glyceraldehyde. 

In the newer R/S system of designating chirality, based on the atomic numbers of atoms near the asymmetric carbon, cysteine (and selenocysteine) have R chirality, because of the presence of sulfur (or selenium) as a second neighbor to the asymmetric carbon atom. 
The remaining chiral amino acids, having lighter atoms in that position, have S chirality. Replacing sulfur with selenium gives selenocysteine.

The majority of Cysteine hydrochloride is obtained industrially by hydrolysis of animal materials, such as poultry feathers or hog hair.
Despite widespread rumor, human hair is rarely a source material.
Indeed, food additive or cosmetic product manufactures may not legally source from human hair in the European Union.
Some animal-originating sources of Cysteine hydrochloride as a food additive contravene kosher, halal, vegan, or vegetarian diets.

To avoid this problem, synthetic Cysteine hydrochloride, compliant with Jewish kosher and Muslim halal laws, is also available, albeit at a higher price.
The typical synthetic route involves fermentation with an artificial E. coli strain.
The Cysteine hydrochloride group is nucleophilic and easily oxidized. 

The reactivity is enhanced when the thiol is ionized, and cysteine residues in proteins have pKa values close to neutrality, so are often in their reactive thiolate form in the cell.
Because of its high reactivity, the sulfhydryl group of cysteine has numerous biological functions.
Cysteine hydrochloride is widely used in the pharmaceutical, cosmetic, and food industries because of its antioxidant and stabilizing functions. 

In medicine, it can be administered as a nutritional supplement, particularly in parenteral nutrition solutions, to provide essential sulfur-containing amino acids for patients who cannot eat normally. 
In the food industry, cysteine hydrochloride is often applied as a flavor enhancer or a dough conditioner in bakery products, where it helps improve dough elasticity and texture. 
In cosmetics and hair-care formulations, it may be included to strengthen hair, promote keratin production, or act as an antioxidant to protect against oxidative stress.

From a biochemical perspective, Cysteine hydrochloride serves as a precursor for glutathione synthesis, which is one of the body’s most important natural antioxidants that helps defend cells against damage caused by free radicals and toxins. 
Because of its reducing properties, it is also employed in laboratory and industrial settings to prevent oxidation of sensitive compounds.

Uses Of Cysteine hydrochloride:
Cysteine hydrochloride, anhydrous is widely used as additive in food production. 
Cysteine hydrochloride is used as an antioxidant to promote fermentation and keep the flavor. 
Cysteine hydrochloride is also used in cosmetics and animal feed.

Cysteine hydrochloride has a wide range of uses across medicine, nutrition, food technology, cosmetics, and industry, because its chemical structure allows it to act as both a source of the essential amino acid cysteine and as a powerful reducing agent.
In the medical and pharmaceutical field, cysteine hydrochloride is commonly included in intravenous (IV) or parenteral nutrition solutions for patients who cannot obtain enough nutrients through normal food intake, since it supplies a readily available source of cysteine, which is necessary for protein synthesis, metabolic processes, and the production of glutathione. 

Cysteine hydrochloride may also be used as a supplement to help support liver detoxification, promote wound healing, and maintain the health of skin, hair, and connective tissues.
In the food industry, cysteine hydrochloride is often added as a processing aid, particularly in bakery and flour-based products, where it functions as a dough conditioner by breaking disulfide bonds in gluten proteins, which softens the dough, makes it easier to knead, and improves the final texture of bread or pastries. 

Cysteine hydrochloride may also be applied as a flavor modifier in savory products, since it can contribute to the development of characteristic roasted or meaty flavors during cooking through Maillard reactions.
In the cosmetic and personal care industry, cysteine hydrochloride is used in products designed to improve hair strength and manageability, since cysteine is a fundamental component of keratin, the protein that makes up hair and nails. 

Cysteine hydrochloride can also act as an antioxidant ingredient in skincare products, where it helps neutralize free radicals and reduce oxidative stress on the skin.
Finally, in biochemical and industrial applications, cysteine hydrochloride is employed as a reducing agent in laboratory experiments to prevent unwanted oxidation of sensitive compounds, and it may also serve as a building block in the synthesis of certain pharmaceuticals and biochemical reagents.

Cysteine hydrochloride is an extremely versatile compound, and its uses span multiple disciplines, from medicine and clinical nutrition to food technology, cosmetics, pharmaceuticals, and biochemical research. 
Because it is the stable hydrochloride salt form of the amino acid cysteine, it is easier to handle, store, and formulate than pure cysteine, while still retaining all of the biological and chemical functions of the parent amino acid.

One of the most important applications of cysteine hydrochloride is in parenteral nutrition (intravenous feeding). 
Critically ill patients, premature infants, and those unable to eat or absorb nutrients properly often rely on IV nutrition, and cysteine hydrochloride provides them with a crucial source of cysteine, which the body cannot synthesize in sufficient amounts under stress. 
This is particularly important because cysteine is a precursor to glutathione, the body’s most powerful antioxidant, which protects cells from oxidative damage, supports immune defense, and enhances detoxification in the liver. 

Without cysteine supplementation, patients may suffer from reduced protein synthesis, weakened antioxidant capacity, and impaired recovery.
In addition to nutrition, cysteine hydrochloride has been studied as a supportive therapy in liver diseases, since it helps replenish glutathione levels that are often depleted in conditions such as cirrhosis or drug-induced liver injury. 
In some cases, it is used as an antioxidant supplement in medical formulations to reduce oxidative stress in tissues. 

Because cysteine is also essential for the production of keratin and collagen, cysteine hydrochloride may play a role in treatments designed to promote wound healing, skin regeneration, and tissue repair.
Cysteine hydrochloride is widely used as a food additive and processing aid, especially in the baking industry. 

Cysteine hydrochloride acts as a dough conditioner by reducing the strength of gluten proteins, which makes dough more pliable, easier to knead, and faster to process. 
This property is especially valuable in large-scale industrial breadmaking, where efficiency and consistency are essential. 
The result is softer bread, better volume, and a more desirable texture.

Safety Profile Of Cysteine hydrochloride:
Moderately toxic by intraperitoneal, intravenous, and possibly other routes, mutation data reported. 
When heated to decomposition Cysteine hydrochloride emits very toxic fumes of NOx, SOx, and Cl-.

Cysteine hydrochloride is generally considered low in toxicity when used properly in medical, nutritional, or cosmetic formulations, but like many amino acid derivatives, it may still pose certain risks depending on the amount, the method of exposure, and the individual’s health condition. 
Cysteine hydrochloride is often recognized as safe in regulated doses (such as in food additives or intravenous nutrition), yet mishandling, overexposure, or accidental misuse can cause irritation, metabolic imbalances, or other health concerns.

In its pure powdered form, cysteine hydrochloride can be an irritant. 
If inhaled, fine dust may cause coughing, throat irritation, and discomfort in the respiratory tract, especially for individuals with asthma or pre-existing lung conditions. 
Direct contact with the skin may lead to mild irritation or dryness, while contact with the eyes can cause redness, tearing, and stinging sensations. 

For this reason, protective gloves, goggles, and dust masks are recommended when handling bulk amounts in laboratories or industrial environments.
While cysteine hydrochloride is used as a supplement or food additive, excessive intake may cause digestive disturbances such as nausea, vomiting, or diarrhea. 

Very high doses may disrupt amino acid balance in the body, potentially leading to metabolic strain on the liver and kidneys, which are responsible for amino acid processing. 
In medical settings, intravenous solutions containing cysteine hydrochloride must be carefully dosed, since too much cysteine can cause acid–base imbalances, hypercysteinemia (excess cysteine in the blood), or even contribute to neurological effects if not properly controlled.