Ergothioneine as a nutraceutical antioxidant: sustainable production, food applications and delivery systems

Ergothioneine (EGT) is a multifunctional antioxidant exhibiting reactivity toward reactive oxygen and nitrogen species, metal-chelating capacity, and transporter-mediated cellular accumulation. Edible mushrooms are rich dietary sources, while microbial biosynthesis offers opportunities for sustainable production. This critical narrative review examines EGT chemistry, biological mechanisms, production, and applications within food systems as well as cosmeceutical/pharmaceutical fields, focusing on studies reporting production, preservation, or formulation outcomes. Special emphasis is placed on inhibiting lipid oxidation, enzymatic browning, and pigment degradation in meat, seafood, and plant-based products. Advances in delivery systems, including nanocarriers designed to enhance stability, bioavailability, and functional performance in fortified foods and active packaging are discussed. However, heterogenous studies, limited clinical evidence, and uncertain long-term safety constrain its translation, and limit firm conclusions of this review. Future priorities include standardization of methods to measure EGT in food, well-designed clinical trials, and regulatory frameworks for nanoformulated EGT, to support food and nutraceutical applications.