Alpha-Tocopherol (alpha-Toc) and its derivatives inhibit tyrosinase in vitro and melanogenesis in epidermal melanocytes. The antioxidant properties of alpha-Toc,
which interferes with lipid peroxidation of melanocyte membranes and increases the intracellular glutathione content, could explain its depigmenting effect. Alpha-Toc has a more effective and long-lasting antioxidant response. Topical application of alpha-Toc and AsA, in vivo, decreases the tanning response inhibiting the UV-induced melanogenesis and proliferation of melanocytes. An alternative compound is alpha-Tocopherol ferulate (alpha-Toc-F), a derivative of alpha-Toc linked by an ester bond to ferulic acid, an antioxidant, which provides stabilization to alpha-Toc, similar to AsA. Alpha-Toc inhibited melanogenesis in cultured normal human melanocytes, although it did not influence melanin synthesis in enzyme solution prepared as cell homogenates. In addition, alpha-Toc stimulated intracellular glutathione (GSH) synthesis (46).
Thirty p/ml of alpha-TF dissolved in 150 pg/ml of lecithin inhibited melanization significantly without inhibiting cell growth. No significant effect on DOPA chrome tautomerase (DT) activity was observed (47).