Enhancement of Topical Delivery and Photostability of Orobol-loaded Microemulsion and Nanostructured Lipid Carriers

Abstract

Isoflavone is a phytochemical mainly found in soybeans and is attracting attention due to its antioxidant and anticancer effect. In particular, orobol, which is the metabolite of genistein, has been found to show excellent efficacy against skin diseases compared with other isoflavones. Orobol was hard to find in the nature, but in recent years, it succeeded in mass production, which enabled production with an affordable price. Therefore, it is attracting attention as a functional cosmetic material of the future. However, there are two major problems in commercialization of orobol. First, orobol has poor photostability. Orobol reacts with organic solvents and causes discoloration when exposed to sunlight. In addition, since it is hydrophilic (log Kow = 2.36), the skin absorption rate is low. For these reasons, formulations overcoming defaults are necessary to enhance the performance of the orobol. In this study, microemulsion and nanostructured lipid carrier were used to formulate nanoparticles to solve the problems of orobol and to maximize its functionality. Microemulsion formulations were prepared by selecting Capmul MCM as an oil phase, Transcutol as a surfactant, and Labrasol as a cosurfactant. Nanostructured lipid carrier was selected from cocoa butter as a solid lipid, Capmul MCM as an oil phase, Tween 20 and Transcutol were used as surfactant. Each particle size and polydispersity were measured and the image of the formulations was observed by TEM. In vitro experiments using Franz diffusion cell at 37 ℃ were performed to assess the extent of skin deposition of the orobol-loaded formulations. Both ME and NLC showed an increase in the amount of skin deposition compared to the standard formulation, and NLC showed up to 6 times higher deposition amount due to the occlusion effect than ME. After exposing sunlight for 5 days to analyze the photostability, ME showed discoloration, but NLC retained color. In addition, the encapsulation efficiency of orobol in NLC is better than that of ME. This indicates that the NLC formulation exhibits more suitable vehicle as a cosmetic formulation of orobol.