Abstract
Cysteine is a sulfur-containing amino acid that plays a central role in skin physiology through thiol-mediated redox regulation and glutathione (GSH) synthesis. It critically influences melanogenesis, collagen homeostasis, and wound healing. However, its clinical application is limited by poor stability and bioavailability. In this review, we provide a mechanistic and comparative analysis of cysteine and its derivatives, including N-acetylcysteine (NAC), cysteinamide (C-NH(2)), GSH, and related compounds. These derivatives regulate melanogenesis by modulating dopaquinone pathways and tyrosinase activity, maintain collagen balance by preserving redox-sensitive enzymatic processes, and enhance wound healing through antioxidant and anti-inflammatory mechanisms. Importantly, chemical modifications such as acetylation, amidation, and esterification improve pharmacokinetic properties, enabling more effective intracellular delivery. Furthermore, different derivatives exhibit distinct advantages depending on biological context, highlighting the importance of compound selection. Overall, cysteine derivatives emerge as promising therapeutic candidates for dermatological applications, particularly in pigmentation disorders and impaired wound healing. Future studies should focus on in vivo validation and clinical translation.