L-Cysteine Monohydrochloride is a chemical compound,  salt of the amino acid cysteine.

The name describes the structure of the molecule.

• L-Cysteine. An amino acid, the "L" denotes the levorotatory form of the amino acid, which is the biologically active form commonly found in proteins.
• Monohydrochloride indicates that the molecule contains a single (mono) chlorine atom (chloride) and a hydrogen atom, forming a hydrochloride salt.
• Description of raw materials used in production.
• Cysteine can be obtained through fermentation processes using engineered bacterial strains or can be extracted from sources like feathers, human and hog hair, or other animal proteins. Hydrogen chloride is the other key raw material used to produce the monohydrochloride.

Step-by-step summary of industrial chemical synthesis process.

• Extraction or Fermentation. L-cysteine is extracted or fermented.
• Neutralization. L-cysteine is then neutralized using sodium hydroxide.
• Acidification. The L-cysteine solution is acidified with hydrogen chloride to form cysteine monohydrochloride.
• Crystallization. The monohydrochloride is crystallized and subsequently dried.
• Purification and Packaging. The crystallized product is purified, quality-checked, and finally packaged.

Form and color. L-Cysteine monohydrochloride appears as a white crystalline powder.

Commercial applications. 

This compound is used across various sectors, including the food industry as a dough conditioner for bread and other baked goods. It also finds application in areas like cosmetics and pharmaceuticals, as well as in nutritional supplements and biotechnology.

Dietary Supplement. L-Cysteine monohydrochloride is used as a supplement to improve hair, skin, and nail health.

Baking. Used as a baking improver to help condition dough and enhance bread texture.

Pharmaceutical Manufacturing. Used in the production of pharmaceuticals and supplements, especially those targeting respiratory system health and nail, hair, and skin health.

Cosmetics and Skin Care. Used in some skincare and hair care products for its antioxidant and regenerating properties.

Food Industry. Used as a food additive to improve dough workability and final product quality.

L-cysteine is an optically active L-form of cysteine. It is obtained industrially from animal products (keratin), but can also be obtained by hydrolysing human hair.

Cysteine is the α-mercaptomethyl (α-thiomethyl)-substituted amino acid of proteins. It is an α-amino acid.

Amino acids play a key metabolic function in the human body and are constituents of proteins.

As food additives they perform different functions: preservatives, flavour enhancers, food supplements and more.

Amino acids together with their salts are used in cosmetics as conditioning agents for both hair and skin (e.g. as moisturisers and other similar functions). Moisturisers are different in nature: the best are the natural ones that exploit the mechanism of integration between the ingredient and the skin by moisturising the horny hydrolipid film, i.e. the thin protective layer that covers the epidermis protecting it from harmful external microbes, keeping the skin moisturised and supple and its pH or acidity value between 4 and 6. Then there are the occlusive moisturisers, usually derived from petroleum (Paraffinum, Paraffinum liquidum and others), but also triglycerides, lanolin oil, natural or synthetic waxes, fatty acid esters and others that create an artificial occlusive layer on the stratum corneum of the skin with the advantage of accelerating the protective process but with the disadvantage of preventing the skin's natural transpiration.

α-amino acids that have similar physical structures undergo similar changes with regard to solubility in water/ethanol mixtures, and technologies to separate α-amino acids from industrial residues, which may not even be innocuous, are constantly being improved. However, many data on the solubility in water-ethanol and ethanol of some α-amino acids are contradictory or even lacking, and the effects of ethanol on the solubility of amino acids may be different. Overall, the scientific literature considers that α-amino acids do not pose significant problems for human health when taken orally, except in people with certain genetic diseases.

• Molecular Formula  C₃H₈ClNO₂S
• Molecular Weight   157.62 g/mol
• CAS  52-89-1
• UNII    A9U1687S1S
• EC Number 200-157-7
• DTXSID0020367