l-cystine

l-cystine is a sulfur-containing amino acid formed by the oxidation of two molecules of l-cysteine linked by a disulfide bond. It serves as a primary structural component of keratin, making it a common ingredient in nutraceutical formulations for hair and nail health, particularly for androgenetic alopecia (AGA). Beyond its structural role, l-cystine is a critical precursor for the synthesis of the antioxidant glutathione. It is transported into cells via the xCT system (the SLC7A11/SLC3A2 glutamate-cystine antiporter), where it is reduced to cysteine. Emerging research indicates l-cystine may alleviate necrotizing enterocolitis (NEC) by inhibiting ferroptosis and balancing Th17/Treg responses through the IL-6/STAT3 pathway. While used therapeutically for hair loss and studied for gastrointestinal protection, l-cystine is also clinically significant in cystinuria, a condition where impaired renal transport leads to the formation of l-cystine stones in the urinary tract.

Other names

cystineL-(-)-cystine(R,R)-3,3'-dithiobis(2-aminopropanoic acid)dicysteine