| Glycyrrhizin (GL), one of the main components extracted from Glycyrrhiza glabra L, which is flavonoids consisting of two molecules of glucuronic acid and one molecule of glycyrrhetinic acid (Metabolites). GL possesses a variety of pharmacological effects, including anti-inflammatory, antiviral and antioxidative activities, etc. and GL is often used for the treatment of liver dysfunction in clinic. However, as poorly water-soluble active ingredient of TCM. due to forming aggregates easily in water, and the poor permeability of gastrointestinal, poor absorption and oral bioavailability has seriously limited the clinical efficacy of GL. In this study, GL was chosen as the model drug, using the mixed micelles technology, to offer the possibility to improve the clinical efficacy of poorly water-soluble drugs by studying its new drug delivery system.Glycyrrhizin-phospholipid/bile salts-mixed micelles (GL-SDC/PL-MMs) was prepared by a film dispersion method, then optimized formulation by central composite design/response surface method, and the best preparation process was determined ultimately:1.19g Phospholipid was dissolved in absolute ethyl alcohol by ultrasonic method. A lipid film was formed after evaporation of ethyl alcohol by rotary evaporator, and then1.0g sodium deoxycholate was dissolved in phosphate buffer (pH=7.4) to get15mmol·L-1mixed solutions. The lipid film was then hydrated, and dispersed in the mixed solutions to form SDC/PL-MMs by ultrasonic method in45℃water bath. Add excess GL to SDC/PL-MMs. nitrogen sealed, mixing24h on a magnetic stirrerto form clarified drug-loaded SDC/PL-MMs, viz., GL-SDC/PL-MMs.The physical and chemical properties and preliminary stability of GL-SDC/PL-MMs were studied. The mean particle size of GL-SDC/PL-MMs was (82.99±7.51) nm with a narrow distribution (PI=0.096±0.015), and zeta potential was (-32.23±1.05) mV. SEM showed the mixed micelles are round or oval, and the particle size correspond to the range described by laser particle size analyzer. The determination of CMC of GL-SDC/PL-MMs by the fluorescent probe method, the results showed CMC was0.0025g/L, which indicating good anti-dilutive effect when mixed micelles go into the systemic circulation. Storage stability results show that mixed micelles have good stability within90days, but in120days, there are significant changes in particle size, PI, zeta potential and drug loading, indicating which is unstable system.In order to store the GL-SDC/PL-MMs for a longer time, solid process of mixed micelles was studied by selecting drying rate, appearance and size variation difference as indicators. Results showed that fluidized-bed drying, with fastest drying rate, is to get white pellets of uniform size, and colorless and transparent solution was got after reconstitution. There are smallest particle size changes before and after drying, and it’s a stable and feasible method with good reproducibility. Therefore, the fluidized bed drying technology was chosen as the best method of solid process of mixed micelles.In this study, the dissolution behavior of DP-GL-SDC/PL-MMs and Glycyrrhizin were compared by establishing the method to determine Glycyrrhizin in vitro dissolution. Results showed the cumulative dissolution rate of DP-GL-SDC/PL-MMs was96.72%in60min, while the maximum cumulative dissolution rate of Glycyrrhizin was only50.69%, which indicating that dissolution rate has been markedly improved after GL was prepared into SDC/PL-MMs.In order to investigate the bioavailability of GL-SDC/PL-MMs, HPLC method to determine plasma concentration of GA was established, and pharmacokinetics of GL-SDC/PL-MMs was studied by choosing Glycyrrhizin and Diammonium Glycyrrhizinate capsules (DGL) as the reference drugs. Since the plasma concentration of GA in Glycyrrhizin group in the same dose is less than the minimum detection line by HPLC, so the plasma concentration-time data of GL-SDC/PL-MMs group and DGL group processing by DAS2.0pharmacokinetic software. The results showed that the pharmacokinetic behavior of GL-SDC/PL-MMs in rats conform with the two-compartment model. Compared with DGL group, Cmax in GL-SDC/PL-MMs group was increased to (77.26±8.20)μg·mL-1from (18.73±7.55)μg·mL-1, while AUC0-24was increased to (343.288±25.88)μg·mL-1·h. from (121.8±10.53) μg·mL-1·h, which indicating GL-SDC/PL-MMs was more easily absorbed relative to DGL and Glycyrrhizin, and bioavailability of Glycyrrhizin was significantly improved by GL-SDC/PL-MMs.In order to study the role of GL-SDC/PL-MMs in treatment of liver injury, acute liver injury model was established by ip CCL4, and then to observed the effect to ALT and AST of GL-SDC/PL-MMs by choosing bifendate as a positive control and the Glycyrrhizin and DGL as the reference formulation. The results show that the GL-SDC/PL-MMs has a good therapeutic effect to acute liver injury induced by CCL4, which has no significant difference with bifendate control group, and the therapeutic effect was significantly better than DGL and Glycyrrhizin.In summary, After Glycyrrhizin, which is poorly water-soluble drug, was prepared into SDC/PL-MMs, the in vitro dissolution and in vivo bioavailability and therapeutic effect on-acute liver injury induced by CCl4has been significantly improved. Accordingly, the mixed micelle technology which is applied to the poorly water-soluble drug delivery system, is an effective way to solve the Poor dissolved in vitro and oral bioavailability of water-soluble drug. |
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