Abstract: Aim To develop an HPLC method with fluorescence detection for the assay of DL111-IT in rabbit plasma. Methods DL111-IT and internal standard glybenzcyclamide in rabbit plasma were extracted with chloroform. The determination was performed on a Diamonsil ODS-C18 column (150 mm×4.6 mm, 5 μm) with a mobile phase of acetonitrile and 0.025 mol·L^-1 diammonium hydrogen phosphate buffer (pH 5.0, adjusted by phosphoric acid) (60:40, V/V) at a flow-rate of 1.0 mL·min^-1. Fluorescence detector was operated at excitation wavelength of 250 nm and emission wavelength of 332 nm. Results The calibration curve in plasma was linear from 1.00-20.00 ng·mL^-1 (r = 0.9996, n = 5).The method afforded average extracting recoveries of 85.3%±1.3%, 84.9%±2.7% and 85.8%±1.8%, and the average method recoveries were 99.5%±0.4%, 102.1%±1.8% and 101.3%±2.4% for the high (20.00 ng·mL-1), middle (10.00 ng·mL^-1) and low (1.00 ng·mL^-1) check samples, respectively. The intra-day (n = 5) and inter-day (n = 5) precisions (RSD) were less than 3.0% and 7.0%, respectively. The limit of detection and quantitation for the method were 0.3 ng·mL^-1 (S/N = 3) and 1 ng·mL^-1 (S/N = 10, RSD<7.0%) plasma sample, respectively. Conclusion The developed method was accurate, sensitive, simple and could be used for pharmacokinetic study of DL111-IT.

Key words: diphenytriazol, diphenytriazol, contragestazol, contragestazol, DL111-IT, DL111-IT, HPLC, HPLC, fluorescence detection, fluorescence detection, pharmacokinetics, pharmacokinetics, glybenzcyclamide, glybenzcyclamide