Interaction of sesamol (3,4-methylenedioxyphenol) with tyrosinase and its effect on melanin synthesis

Sesamin, sesamolin (lignans) and sesamol from sesame seed (Sesamum indicum L.) - are known for their health promoting properties. We examined the inhibition effect of sesamol, a phenolic degradation product of sesamolin, on the key enzyme in melanin synthesis, viz. tyrosinase, in vitro. Sesamol inhibits both diphenolase and monophenolase activities with midpoint concentrations of 1.9 mu M and 3.2 mu M, respectively. It is a competitive inhibitor of diphenolase activity with a K-1 of 0.57 mu M and a noncompetitive inhibitor of monophenolase activity with a K-i of 1.4 mu M. Sesamol inhibits melanin synthesis in mouse melanoma B16F10 cells in a concentration dependant manner with 63% decrease in cells exposed to 100 mu g/mL sesamol. Apoptosis is induced by sesamol, limiting proliferation. This study of the chemistry and biology of lignans, in relation to the mode of action of bioactive components, may open the door for drug applications targeting enzymes. (C) 2010 Elsevier Masson SAS. All rights reserved.