Microemulsion formulation design and evaluation for hydrophobic compound: Catechin topical application

Abstract The aim of the present study was to design a microemulsion for catechin topical application. A mixture experimental design with five independent variables (X 1 : oil, X 2 : surfactant, X 3 : catechin, X 4 : cosurfactant and X 5 : water) was developed, and the response surface methodology was used to study the effect of formulation components on physiochemical characteristics and penetration capacity of a catechin-loaded microemulsion, and to obtain an optimal microemulsion formulation. The results showed that the drug-loaded microemulsion formation and characteristics were related to many parameters of the components. The transdermal amounts in receiver cells and skin deposition amount remarkably increased about 4.1–111.6-fold and 0.6–7.6-fold respectively. The lag time was significantly shortened from 10 h to 1.0–6.7 h. The optimal formulation with 20% surfactant, 30% cosurfactant and 2.6% Catechin was subjected to stability and irritation tests. The results showed that the physicochemical characteristics and catechin level of the drug-loaded microemulsion did not show significant degradation after 3 months of storage at 25 °C.The catechin-loaded microemulsion did not cause significant irritation compared to the water-treated group.