L-Cystine dihydrochloride, with the CAS number 30925-07-6, is a hydrochloride derivative of L-cystine, also known as (R,R)-3,3′-Dithiobis(2-aminopropanoic acid) dihydrochloride. Its molecular formula is C₆H₁₄Cl₂N₂O₄S₂, and its molecular weight is 313.22 g/mol. It is formed by the reaction of L-cystine with hydrochloric acid, retaining the natural L-configuration and disulfide bond core structure, while significantly improving water solubility and chemical reactivity, making it widely applied in pharmaceuticals, nutritional supplements, biochemistry research, and fine chemical production.
Physically, L-Cystine dihydrochloride appears as a white to off-white crystalline powder or granular solid. It has a melting point of approximately 205-210℃ (decomposition) and is highly soluble in water, forming a clear aqueous solution, while soluble in polar organic solvents such as methanol and ethanol, and slightly soluble in dimethylformamide. It is optically active, with a specific rotation [α]²⁰/D of -195° to -205° (in water, c=1). It has moderate hygroscopicity and remains stable under normal temperature and pressure when stored properly, facilitating easy handling, storage, and formulation into various dosage forms such as tablets, capsules, and oral solutions.
Chemically, the dihydrochloride salt form enhances its solubility and reactivity compared to free L-cystine. Its core disulfide bond is stable under neutral and weakly acidic conditions but can be reduced to two L-cysteine molecules under reducing environments, participating in the body’s redox balance. It contains two amino groups and two carboxyl groups, enabling it to participate in peptide bond formation and various biochemical reactions, serving as an ideal chiral building block for organic and peptide synthesis.
Its core applications focus on pharmaceuticals, nutritional supplements, and biochemistry research. In the pharmaceutical industry, it is used as a raw material for preparing amino acid supplements, drugs for treating cystine deficiency, and liver-protective agents, helping to maintain the body’s sulfur balance and support cellular metabolism. In nutritional supplements, it is added to health products to enhance immunity, promote hair, skin, and nail health, and support antioxidant defense.
In biochemistry research, it is used as a biochemical reagent for studying protein structure, redox reactions, and amino acid metabolism. Safety-wise, it is generally recognized as safe under normal handling and dosage, non-toxic and non-irritating. It should be stored in a sealed, cool, dry, and dark environment, away from oxidants, moisture, and high temperatures to prevent oxidation and decomposition. With its high solubility, good biocompatibility, and versatile applications, it is a valuable raw material in the health care and life science industries.
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