Evaluation of the incorporation of essential oils in microemulsions as a promising formulation in the inhibition of tyrosinase

Abstract The present work aimed to develop and characterize a microemulsion containing an essential oil with potential skin-lightening activity. Initially, Cinnamomum zeylanicum Blume essential oils (CZEO) extracted from bark and leaf, and the essential oils of Citrus sinensis and Syzygium aromaticum, were characterized and the tyrosinase inhibitory activity was determined. Thereafter, microemulsions were obtained through the Pseudoternary Phase Diagram using a mixture of Tween 80®: Propylene glycol (2:1) as surfactant and co-surfactant, respectively, Olivem 300® as oily phase and water as aqueous phase. The CZEO from the bark showed higher tyrosinase inhibitory activity and was incorporated into the selected microemulsions: one o/w microemulsion (B7) and three bicontinuous microemulsions (B5, B6 and C6). Microemulsion B5 was able to incorporate a greater amount of essential oil and the tyrosinase inhibitory activity of this formulation was determined. Microemulsions with and without the essential oil were isotropic with a droplet diameter lower than 60 nm and Newtonian behavior. Microemulsion B5 showed significant greater tyrosinase inhibition activity and lower cytotoxicity than did the isolated oil. According to the results, the microemulsions containing the CZEO obtained from the bark may be promising in formulations for skin lightening using natural active agents.