N-acetyl glucosamine and niacinamide block melanin production by interfering in the process at two different points - reducing formation and appearance of age spots. A key enzyme in melanin biosynthesis is tyrosinase. It is initially produced in the cell as an inactive pro-enzyme, which is then glycosylated to the active form. While n-acetyl glucosamine (a sugar itself) is not a direct inhibitor of tyrosinase, it does inhibit the activation of the enzyme, resulting in a decrease in melanin. Niacinamide inhibits the transfer of melanin-containing melansomes to the outer layers of skin, helping prevent the formation of an age spot.