This work developd nanomaterials formulated from annatto seed oily extract (ASE), myristic acid (tetradecanoic acid), and their fatty acid esters. The annatto seed oily extract was obtained using ...only soybean oil (ASE + SO) and Brazil nut oil (ASE + BNO). The UV/VIS analysis of the oily extracts showed three characteristic peaks of the bixin molecule at 430, 456 and 486 nm. The lipid nanoparticles obtained using myristic acid and ASE + BNO or only BNO showed better results than the oil soybean extract, i.e., the particle size was <200 nm, PDI value was in the range of 0.2−0.3, and had no visual physical instability as they kept stable for 28 days at 4 °C. Lipid nanoemulsions were also produced with esters of myristic acid and ASE + BNO. These fatty acid esters significantly influenced the particle size of nanoemulsions. For instance, methyl tetradecanoate led to the smallest particle size nanoemulsions (124 nm), homogeneous size distribution, and high physical stability under 4 and 32 °C for 28 days. This work demonstrates that the chemical composition of vegetable oils and myristic acid esters, the storage temperature, the chain length of fatty acid esters (FAE), and their use as co-lipids improve the physical stability of lipid nanoemulsions and nanoparticles from annatto seed oily extract.
•Cinnamomum essential oil from bark (CZEO_B) was the most effective essential oil.•Microemulsion (ME) containing CZEO_B and Olivem 300 was obtained.•Synergism between Olivem 300 and CZEO_B was ...observed in the ME.•ME was also able to significantly decrease the cytotoxicity of CZEO_B.•ME containing Olivem 300 and CZEO_B can be a promising formulation for skin lightening.
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.
