👉 Menadione is a type of antioxidant found in certain types of fish and shellfish. It has been used as an anti-aging agent for centuries, but its exact mechanism of action is still not fully understood. Menadione is produced during the process of cooking seafood or shellfish. When this protein-rich substance comes into contact with air, it reacts chemically with free radicals in the food to form a protective layer called a "menadione barrier." This structure protects the fish from further