Abstract: To improve the dissolution rate of vitexin, the micronization of vitexin in an antisolvent recrystallization process using N-methylpyrrolidone (NMP) as solvent and water as antisolvent was studied in this paper. The effects of operating parameters including concentrations of vitexin solution, system temperatures, stirring rates and kinds of surfactants (PVP, Tween80, SDS) on the particle size of micronized vitexin were investigated. Particles of micronized vitexin with a mean particle size of 291.1 nm were obtained under the optimized process conditions (vitexin solution concentration 20 mg·mL^-1, volume ratio of antisolvent to solvent 10∶1, stirring rate 1 500 r·min^-1 and concentration of PVP 8 mg·mL^-1). The processed vitexin particles and the unprocessed one were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fouriertransform infrared spectroscopy (FT-IR). The results showed that antisolvent recrystallization process did not induce degradation of vitexin and the micronized vitexin had lower crystallinity. The chemical properties of the processed vitexin did not change when compared with the original drug, and there was a significant increase of the dissolution rate of the processed vitexin comparing with the unprocessed vitexin.

Key words: vitexin, antisolvent recrystallization, micronization, dissolution