Preparation of a bis-demethoxy curcumin microemulsion based on pseudo-ternary phase diagrams and an orthogonal test analysis

Abstract

A bis-demethoxy curcumin microemulsion was successfully prepared using the method of pseudo-ternary phase diagrams combined with an orthogonal test in a 3-phase system (O phase=active ingredient; S phase=surfactants; W phase=water). The best transparent region for preparing the bis-demethoxy curcumin microemulsion was formed when Termul-200 (an alkylphenol polyether block copolymer emulsifier) and sodium dodecyl benzene sulfonate (SDBS) (4 : 1 w/w) were used as surfactants (S phase), isopropanol (30% in S phase) as a co-surfactant, and a bis-demethoxy curcumin DMF solution (30%) as the active ingredient (O phase). According to the infinite dilution region of the best phase diagram, the best ratio among O, S and W phases for preparing the bis-demethoxy curcumin microemulsion was a weight ratio of 4.5 : 20 : 75.5. Stability tests showed that all the indicators of our prepared microemulsion met the storage stability criteria. Our results suggested that the combination of the pseudo-ternary phase diagram and orthogonal test analysis provided an effective approach for designing a microemulsion formulation.