Development and validation of a liquid chromatography-tandem mass spectroscopy method for simultaneous determination of (+)-(13aS)-deoxytylophorinine and its pharmacologically active 3-O-desmethyl metabolite in rat plasma.

CAT ((+)-(13aS)-deoxytylophorinine) is a novel anticancer drug belonging to phenanthroindolizidine alkaloids. A sensitive and reliable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous quantification of CAT and its pharmacologically active 3-O-desmethyl metabolite (S-4) was developed and validated in rat plasma using rotundine as the internal standard (IS). CAT, S-4 and IS were extracted by acetonitrile protein precipitation and separated on an Eclipse XDB-C18 column (1.8 μm, 4.6 mm × 50 mm) with acetonitrile-water (27:73, v/v) mobile phase containing 0.1% formic acid at a 0.4 mL/min flow rate. Positive ion electrospray ionization in multiple reaction monitoring mode was employed to measure CAT, S-4 and IS by monitoring the transitions m/z 364.2→70.1 for CAT, 350.1→70.1 for S-4 and 356.2→192.2 for IS. Good linear correlation (r(2)>0.991) was achieved for CAT and S-4 over the range of 0.214-128.16 and 0.044-11.00 ng/mL, respectively. The lower limit of quantification was 0.214 ng/mL for CAT and 0.044 ng/mL for S-4, using 50 μL rat plasma samples. The intra- and inter-day precisions were not exceed 15% and the accuracy ranged between 94.80% and 108.22%. The average extraction recoveries of both analytes were greater than 94.62%. The method was successfully applied to the pharmacokinetic study of CAT and S-4 in rats after oral administration.