Development of microemulsion and water/oil/water multiple emulsion containing beta-arbutin, lactic acid, and sodium ascorbyl phosphate

Objective: In addition to lactic acid and sodium ascorbyl phosphate, which have whitening effects, beta-arbutin is a safe whitening agent for skin. Combining these three substances should reduce the concentration of each one in a formula and achieve an optimal whitening effect. In this study, microemulsions and water/oil/water (W/O/W) multiple emulsions were applied to produce a formula containing these whitening agents. Methods: All the active ingredients were formulated into microemulsions and W/O/W multiple emulsions with different concentrations of Tween 80 and Span 80 as emulsifiers to obtain a stable formula. Twelve-week physical stability studies were performed for every formula at low (4±2°C), room (28±2°C), and high (40±2°C) temperatures. Results: The produced microemulsions were transparent with a mean droplet size of 15.50 nm. In addition, the W/O/W multiple emulsions contained droplets within droplets, which were dispersed in a continuous phase with an inner droplet size of 0.15 nm and an outer droplet size of 0.37 nm. The W/O/W multiple emulsions showed pseudoplastic thixotropic flow properties. Furthermore, the microemulsions were stable at low (4±2°C) and room (28±2°C) temperatures, while the W/O/W multiple emulsions were stable at room (28±2°C) and high (40±2°C) temperatures. Conclusion: It was concluded that the combination of beta-arbutin, lactic acid, and sodium ascorbyl phosphate was suitable for formulating into microemulsions as well as W/O/W multiple emulsions as whitening cosmetic products.