Optimization of preparation technology for Acanthopanax senticosus total saponins microemulsion by D-optimal mixture design and intestinal absorption characteristics

Abstract

Following the preparation of Acanthopanax senticosus total saponins microemulsion, the formulation and preparation technology were optimized and the quality was evaluated. The absorption characteristics of A. senticosus total saponins microemulsion by the self-microemulsifying drug delivery system(SMEDDS) were investigated in the unidirectional intestinal perfusion model in vivo. The oil phase, mass ratio(K_m), number of revolutions, and drug concentration were subjected to single-factor investigation with the area of pseudo-ternary phase diagram as the index. The process was optimized by D-optimal mixture design with the particle size as the index, and then the appearance, morphology, and particle size were investigated. The mass concentrations of eleutherosides B and E in the microemulsion were determined. The results showed that the optimum formulation of A. senticosus total saponins microemulsion was determined as follows: 20.8% of water phase, 31.2% of isopropyl palmitate, and 48.0% of soybean phospholipid and absolute ethanol(K_m=1∶1). As revealed by the observation under a transmission electron microscope, the microemulsion exhibited homogeneous dispersion and was a spherical emulsion droplet in the water-in-oil type. At room temperature, the pH value was 5.19, the refractive index 1.416 5, the average particle size(26.47±0.04)nm, and the polydispersity index(PDI) 0.118±0.03. The content of the eleutherosides B and E was 0.038 9 and 0.166 4 mg·mL~(-1), respectively. The preliminary stability study showed that the solution was clear and transparent within 30 d, without stratification or content change, indicating good stability. The absorption of microemulsion in each intestinal segment was significantly improved as compared with that of the A. senticosus total saponins, with the best absorption effect detected in the ileum, which has laid a foundation for further development and utilization of A. senticosus.