Optimization And Pharmacokinetics Of Emodin Loaded Nanoemulsion

Objective:To development, optimization and evaluation of emodin loaded nanoemulsion (EMO-NE) prepared by ultrasonic emulsification and to investigate the pharmacokinetic properties of EMO-NE in rats.Methods:1. Screening of components of nanoemulsion was according to the solubility studies and pseudoternary phase diagrams of nanoemulsion. EMO-NE was optimized using response surface methodology based on central composite design (CCD-RSM) to investigate the influence of main formulation variables as well as ultrasonic operating parameters on the properties of nanoemulsion prepared by ultrasonic emulsification.2. Quantitative analysis of emodin of nanoemulsion system was performed by high performance liquid chromatography (HPLC) equipped with a diode-array detector. Characters of EMO-NE were determined, and in vitro drug release properties of EMO-NE and emodin suspension were also analyzed.3. Quantitative analysis of the plasma concentration of emodin was conducted by HPLC equipped with fluorescence detector after rats administered orally EMO-NE and emodin suspension. The pharmacokinetic parameters were calculated using a DAS 3.2.7 pharmacokinetic software to illustrate the pharmacokinetic properties of EMO-NE and emodin suspension in rats.Results:1. Capryol 90, Cremophor RH 40 and Transcutol HP were selected as the oil, surfactant, and cosurfactant of EMO-NE, respectively. Km (Cremophor RH 40/Transcutol HP, w/w) was 2:1. Additionally, the addition of oleic acid used as the stabilizer at mass ratio level of 1%and suitable pH value environment with 6.5 were necessary to impart significant properties of physical stability through increasing zeta potential (ZP) of EMO-NE. Based on CCD-RSM, the optimal variations were 11.84% oil content,20.16% mixed emulsifier content,23.42 min ultrasonic working time and 156 w ultrasonic amplitude. Furthermore, the mathematical model was verified, indicating the actual response values were basically in agreement with the predicted values.2. Visual observation found that the appearance of the optimized EMO-NE was clear, homogeneous and transparent with colour of brown yellow, and the micromorphological shape was spherical. The content of emodin of EMO-NE was 0.487±0.014 mg/ml. The mean viscosity of EMO-NE was 11.87±0.81 cP, a mean%transparency was 99.10±0.02% at a wavelength of 700 nm. Besides, the mean ZP value, droplet size and polydispersity index were-25.2±0.5 mV,20.3±0.5 and 0.151±0.005, respectively. Visual observation did not find coalescence, phase separation and demulsification after a high-speed centrifugation. For stress test of temperature stability and the test of a 60-day storage in the darkness, the droplet size and emodin content were nearly unchangeable excluding stress test of photostability with the content of emodin lost about 5.88% on the 10th day compared to that of the first day.80.79±1.11% of emodin released from EMO-NE at the end of 120 h, exhibiting obvious sustained release property and the drug releasing mechanism was comparatively fitted to Higuchi equation (R2=0.9604±0.0007).3. The main pharmacokinetic parameters of emodin suspension including Tmax, Cmax, MRT0-∞, t1/2zand AUCo-∞. were 0.75 h,74.905 ng/ml,5.352 h,2.710 h and 417.789 ng·h/ml, respectively, while the main pharmacokinetic parameters described above of EMO-NE were 1.0 h,120.988 ng/ml,13.246 h,12.904 h and 993.869 ng·h/ml obtained with application of statistical moment method, indicating which were 1.62-foldincreased in Cmax,4.76-fold increased in t1/2z, 2.47-foldincreased in MRTV0-∞,2.38-fold increased in AUC0-∞ compared to these parameters calculated from EMO suspension.Conclusion:1. The components of nanoemulsion screened led to the formation of nanoemulsion easier and the area of oil-in-water nanoemulsion region larger. The optimized EMO-NE had clear, homogeneous and transparent appearance with spherical micromorphological shape, small droplet size, narrow size distribution, low viscosity and good physical and chemical stability. Besides, the in vitro release of emodin from EMO-NE was deduced to be fitted to the Higuchi model.2. Pharmacokinetic study showed EMO-NE obviously possesed sustained-release property, higer plasma concentration, longer residual time, lower elimination time and higher bioavailability.