Enhancement of solubility, antioxidant ability and bioavailability of taxifolin nanoparticles by liquid antisolvent precipitation technique

Taxifolin is a kind of flavanonol, whose antioxidant ability is superior to that of ordinary flavonoids compounds owing to its special structure. However, its low bioavailability is a major obstacle for biomedical applications, so the experiment is designed to prepare taxifolin nanoparticles by liquid antisolvent precipitation (LAP) to improve its bioavailability. We selected ethanol as solvent, deionized water as antisolvent, and investigated primarily the type of surfactant and adding amount, drug concentration, volume ratio of antisolvent to solvent, precipitation temperature, dropping speed, stirring speed, stirring time factors affecting drug particles size. Results showed that the poloxamer 188 was selected as the surfactant and the particle size of taxifolin obviously reduced with the increase of the poloxamer 188 concentration, the drug concentration and the dropping speed from 0.08% to 0.45%, from 0.04 g/ml to 0.12 g/ml, from 1 ml/min to 5 ml/min, respectively, when the volume ratio of antisolvent to solvent increased from 2.5 to 20, the particle size of taxifolin first increased and then decreased, the influence of precipitation temperature, stirring speed, stirring time on particle size were not obvious, but along with the increase of mixing time, the drug solution would separate out crystallization. The optimum conditions were: the poloxamer 188 concentration was 0.25%, the drug concentration was 0.08 g/ml, the volume ratio of antisolvent to solvent was 10, the precipitation temperature was 25 °C, the dropping speed was 4 ml/min, the stirring speed was 800 r/min, the stirring time was 5 min. Taxifolin nanosuspension with a MPS of 24.6 nm was obtained under the optimum conditions. For getting taxifolin nanoparticles, the lyophilization method was chosen and correspondingly γ-cyclodextrin was selected as cryoprotectant from γ-cyclodextrin, mannitol, lactose, glucose. Then the properties of raw taxifolin and taxifolin nanoparticles were characterized by scanning electron microscopy (SEM), fourier-transform infrared spectroscopy (FTIR), high performance liquid chromatography-mass spectrometry (LC-MS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermo gravimetric (TG), and the conclusion was drawn that taxifolin nanoparticles can be converted into an amorphous form but its chemical construction cannot been changed. Furthermore, dissolving capability test, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity and reducing power assay, solvent residue test were also carried out. The experimental data showed that the solubility and the dissolution rate of taxifolin nanoparticles were about 1.72 times and 3 times of raw taxifolin, the bioavailability of taxifolin nanoparticles increased 7 times compared with raw taxifolin, and the antioxidant capacity of taxifolin nanoparticles was also superior to raw taxifolin. Furthermore, the residual ethanol of the taxifolin nanoparticles was less than the ICH limit for class 3 solvents of 5000 ppm or 0.5% for solvents and could be used for pharmaceutical. These results suggested that taxifolin nanoparticles might have potential value to become a new oral taxifolin formulation with high bioavailability.