Determination of diosbulbin B in rat plasma and urine by LC-MS/MS and its application in pharmacokinetic and urinary excretion studies

A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for determination of diosbulbin B in rat plasma and urine after oral administration. The detector was a Q-trap™ mass spectrometer with an electro-spray ionization interface operating in the multiple reaction monitoring mode. After extracted with methyl tert-butyl ether, diosbulbin B and busprione (internal standard, IS) were separated on an Agilent Zorbax C₁₈ column (4.6mm×50mm, 3.5μm) using a gradient mobile phase consisting of water and methanol. Linearity was obtained over the concentration range of 5-5000ng/ml for diosbulbin B in rat plasma and urine. The lower limit of quantitation was 5.0ng/ml. The accuracy (relative error, RE) and precision (relative standard deviation, RSD) of disobulblin B in two biological matrices ranged from -8.2% to 1.4% RE and 1.9 to 10.1% RSD, respectively. The fully validated method was applied to a pharmacokinetic and urine excretion study for the first time. The main pharmacokinetic parameters T_max, C_max, T_1/2, and K_e were 1.88±0.22h, 18.0±3.1ng/ml, 6.89±1.0h and 0.103±0.01l/h, respectively. A cumulative excretion of disobulbin B in rat urine was 2.69±0.43μg at 60h after dosing, accounting for 0.89% of the total dose.