Design and evaluation of a self-microemulsifying drug delivery system for apigenin.

Objective of this study was to prepare, characterize and evaluate a self-microemulsifying drug delivery system (SMEDDS) with the aim to improve the solubility and dissolution of apigenin. Ternary phase diagrams were constructed in order to obtain the most efficient self-emulsification region, and the formulation of apigenin loaded SMEDDS was optimized by a simplex lattice experiment design. The optimal formulation of SMEDDS obtained was comprised of 60% Cremophor(®)EL, 30% Transcutol(®)HP and 10% Capryol™ 90. The equilibrium solubility of apigenin in SMEDDS was about 15 mg/g, and it could increase the solubility of apigenin in water for about 7500 folds. Apigenin loaded SMEDDS could turn into microemulsion when diluted with distilled water and the droplets were spherical under transmission electron microscope (TEM), the average particle size was 17.1 nm and zeta potential -5.18 mV. In vitro dissolution studies showed about 95% of apigenin was released within 10 min. All of the results showed that SMEDDS could enhance the solubility and dissolution of apigenin, and would be a potential carrier to improve the oral absorption of apigenin, a poorly water soluble drug.