Effect of sesamol, a potent tyrosinase inhibitor, on melanin and melanin synthesizing melanoma cells

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The effect of lignans – sesamin, sesamolin and sesamol – from sesame seed (Sesamum indicum L.), known for their health promoting properties, on melanin synthesis was studied using mouse melanoma B16F10 cells. Sesamol inhibited the synthesis of melanin by 63%; sesamin and sesamolin had negligible effects (<2%). Reduction in melanin content of the cells was associated with the concomitant loss of viability and proliferation. The cell survivability could be attributed to the suppression of prooxidant effect of melanin in melanoma cells by the high antioxidant activity of sesamol (IC50 = 5.1 μg/mL). The hindered protective effect of melanin against UV induced skin damage and cancers (via its antioxidant property) in highly proliferative melanoma cells could probably be due to the presence of prooxidant short chain melanin polymers in the latter. To understand the role of lignans in inhibition of melanin synthesis, the effect of sesamol on tyrosinase (EC ), a copper containing oxygenase with mono and diphenolase activities was studied. Sesamol inhibited monophenolase and diphenolase activity in a noncompetitive and competitive manner with Ki values of 1.4 μM and 0.57 μM, respectively. This first ever report of the effect of lignans on melanin synthesis might help in validating the health benefits of sesame lignans.