11

Background: Hyperpigmentation disorders are considered signs of skin aging and are aesthetically unpleasant. Most active ingredients used against hyperpigmentation disorders predominantly target tyrosinase activity. Objectives: To study the effect of two Origanum essential oils on the melanogenic activity of B16-F1 murine melanocytes. The main component of these oils, carvacrol, was also investigated and a model for anti-melanogenic activity is proposed. Materials and Methods: B16-F1 melanocytes were exposed to different concentrations of essential oils and carvacrol. The level of tyrosinase and melanin was determined using spectrophotometric measurements. Results: Essential oils of Origanum syriacum and Origanum ehrenbergii led to a significant 14% and 17% reduction in melanin level at 40 μg mL-1, respectively. However, neither demonstrated a significant effect on the level of intracellular tyrosinase. The same effects were found for carvacrol which led to a 30% reduction in melanin at 45 μg mL-1. Conclusion: Our results indicate that the oils studied are anti-melanogenic. We propose a mechanism, similar to that for hydroquinone, whereby carvacrol functions as a competitive inhibitor of tyrosinase, thus inhibiting oxidation of tyrosine and causing a deregulation of melanogenesis.