Preparation, characterization, and dissolution characteristics of ursolic acid nanoparticles prepared by emulsion solvent evaporation method / 中草药

ABSTRACT

Objective To prepare and characterize ursolic acid nanoparticles (UANs), and to investigate its improvement of equilibrium solubility and dissolution rate. Methods UANs were prepared by emulsion solvent evaporation method, and followed by freeze-drying. The organic phase was trichloromethane containing 30% ethanol, the aqueous phase is ultrapure water, poloxamer 188 was as surfactant and cryoprotectant. The optimal conditions for preparing nanoparticles were screened out using single-factor experiment. The particle size was used as the basis for optimization experiment. The following six main parameters had significant influences on particle size were picked out, including the concentration of poloxamer 188, volume ratio of organic to water phase, homogenate speed and homogenate time, as well as homogenization pressure and cycles. And then, dynamic light scattering equipment was used to analyze the mean particle size, the morphology of UANs powder obtained was presented by scan electronic micro-scope (SEM). The UANs weather and how changes in surface chemical character and physical structure was estimated by using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The equilibrium solubility study and dissolution test were carried on raw ursolic acid (UA) and UANs. Results The optimal conditions of preparation UANs 0.05% of poloxamer 188, 14 of volume ratio of organic to water phase, 7 000 r/min of homogenate speed for 2 min and a homogenization pressure of 50.0 MPa for 6 times. Based on the optimal conditions, the mean particle size was (157.5 ± 28.0) nm and Zeta potential of (20.33 ± 1.67) mV. Particle distribution of UANs illustrated that UA had been nanoscale with uniform particle size distribution. SEM showed that UANs were nearly spherical. By the XRD and DSC, we could acquaint UA in UANs had the same chemical structure as the raw UA but had been amorphous state. The result of solubility test figured that the equilibrium solubility of UANs was 13.48 times in SGF, 11.79 times in SIF and 23.99 times in deionized water than raw UA. The dissolution rate of UANs prepared by ESE method has been up to 14.72 times in SGF and 74.35 times in SIF. Conclusion This study indicates that the emulsion solvent evaporation method has an array of valued on improving water solubility of UA, and it will have benefit on enhancing oral bioavailability.