Objective:To establish an HPLC method to determine the entrapment efficiency (EE) and drug loading (DL) of curcumin (CUR)and quercetin (QUE)loaded self-microemulsifying drug delivery system.Methods:A centrifugation method was used to isolate the free drug.The content of drug was determined by HPLC.The analytical column was a Purospher STAR LP C18 column (250 mm×4.6 mm,5 μm) and the column temperature was 30 ℃.The mobile phase was acetonitrile-4% acetic acid (50∶50) and the flow rate was 1.0 ml·min-1.The UV detection wavelength was set at 370 nm and the injection volume was 10 μl.Results:CUR and QUE were linear within the range of 10.728-96.552 μg·ml-1 (r=0.999 8) and 1.08-9.72 μg·ml-1 (r=0.999 9),respectively.The average recovery was 99.98%(RSD=1.46%,n=9) and 100.34%(RSD=1.06%,n=9),respectively.In CUR-QUE-SMEDDS,the EE of curcumin and quercetin was (95.97±0.50)% and (95.91±2.52)%,and the DL was (25.82±0.15) mg·g-1 and (1.80±0.05)mg·g-1,respectively.Conclusion:The method is accurate,rapid and simple,and suitable for the determination of DL and EE in CUR-QUE-SMEDDS.

The aim of the study was to prepare and evaluate the quality of negatively charged selfmicroemulsifying drug delivery system of curcumin (NC-CUR-SMEDDS).Based on the CUR-SMEDDS,the optimum amount of excipients was confirmed by the single-factor design experiment taking mean particle size,Zeta potential,drug entrapment efficiency and the drug loadings of curcumin as the evaluation indices for the preparation of NC-CUR-SMEDDS.The quality of NC-CUR-SMEDDS was evaluated by observing its appearance status,transmission electron microscope micrographs and determining particle diameter,Zeta electric potential,drug entrapment efficiency and drug loading.As a result,it was found that the Zeta potential reached -43.43 ± 0.29 mV when 4％ docusate sodium was added.The appearance of NC-CUR-SMEDDS remained clarified and transparent,and the microemulsion droplets appeared spherical without aggregation with uniform particle size distribution.The mean particle size was 14.08 ± 0.082 nm,the drug loading of curcumin was 26.48 mg·g-t and the drug entrapment efficiency was 94.12％.It was concluded that NC-CUR-SMEDDS with high entrapment efficiency and uniform particle size distribution met the requirement of inflammatory target binding in the colon.