Preparation of silybin self-nanomicroemulsion containing functional oil and its in vitro evaluation / 中草药

ABSTRACT

Objective: In order to improve the bioavailability of the insoluble drug silybin, silybin supersaturated self- nanoemulsifying drug delivery systems (SLB-S-SNEDDS) containing functional oil were prepared, its characterization and in vitro evaluation were also performed. Methods: Functional oils were screened by performing potassium ferrohydride reduction and 1,1- diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging experiments. The pseudo-ternary phase diagram was drawn to investigate the emulsifying ability of emulsifier. The proportion of mixed oil phase and drug loading capacity were explored by analyzing particle size, polydispersity index (PDI), zeta potential, etc. The type and concentration of supersaturated substance in SLB-S-SNEDDS were obtained by conducting the compatibility and dissolution experiments. SLB-S-SNEDDS was characterized with appearance, particle size distribution, self-emulsification efficiency, and morphology, and its in vitro dissolution, antioxidant capacity, and cytotoxicity were also evaluated. Results: The prescriptions of SLB-S-SNEDDS were as follows (1) wheatgerm oil/Capryol 90- Cremophor ELP-Transcutol HP; (2) seabuckthorn seed oil/Capryol 90-Cremophor ELP-Transcutol HP. One g S-SNEDDS matrix contained 0.043 g of wheatgerm oil or sea-buckthorn seed oil, 0.387 g of Capryol 90, 0.380 g of Cremophor ELP, and 0.190 g of Transcutol HP. The adding amount of silybin in S-SNEDDS prescription was 20% of the sum of the equilibrium solubility of silybin in each component, and the adding amount of Soluplus was 0.1% of the total mass described above. The two obtained SLB-S-SNEDDS were transparent homogeneous liquid with light yellow (wheat germ oil) and bright yellow (seabuckthorn seed oil) color, respectively. After being dispersed, SLB-S-SNEDDS turned into subspherical white flat emulsion droplets with the particle size of about 50 nm, and the emulsification time was 65 s. Compared with raw materials and SLB-SNEDDS, the cumulative dissolution of silybin in SLB-S-SNEDDS was maintained between 85% and 110% within 8 h, indicating that the two systems can significantly improve the dissolution of silybin. The absorbance of SLB-S-SNEDDS after reaction with potassium ferricyanide (0.452-0.782, 0.488-0.765) and the DPPH free radical clearance of SLB-S-SNEDDS (39.09%-96.02%, 30.54%-89.20%) were all higher than those of raw silybin (0.411-0.760, 22.89%-63.21%), which suggested that the two systems can enhance the antioxidant capacity of silybin. Cytotoxicity test results showed that the cell survival rate in silybin raw material group, combination of silybin and S-SNEDDS group, and blank S-SNEDDS group were greater than 90% at 5 µmol/L and 10 µmol/L drug concentration, indicating that SLB-S-SNEDDS and its auxiliary materials were safe and less toxic to human cloned colorectal adenocarcinoma cell line (Caco-2). Conclusion: The SLB-S-SNEDDS containing functional oil prepared in this paper can not only increase the cumulative dissolution of silybin, but also enhance its antioxidant capacity, which provides a useful reference for supersaturated self-nanoemulsifying drug delivery systems (S-SNEDDS) to improve the water-solubility and bioactivity of insoluble drugs.