The purpose of this study was to develop a simultaneous, sensitive and reproducible UPLC-MS/MS method to quantify maackiain and its phase II metabolites, maackiain-sulfate (M-7-S) and maackiain-glucuronide (M-7-G). A Waters BEH C18 column was used with acetonitrile/water as mobile phases. Analysis was performed under negative ionization electrospray mass spectrometer via the multiple reaction monitoring (MRM). The one-step protein precipitation by methanol was used to extract the analytes from plasma. The results showed that the linear response range was 5000-9.75 nM for maackiain, M-7-S, and M-7-G. The lower limit of detection (LLOD) was 4.88 nM for these three analytes. The intra-day variance is less than 12.4% and accuracy is in 85.7-102.0%. The inter-day variance is less than 11.2% and accuracy is in 89.6-122.2%. The analysis was done within 4.0 min. Only 20 μl of blood is needed for the analysis due to the high sensitivity of this method. The validated method was used for pharmacokinetic study in A/J mouse, maackiain Caco-2 cell culture model experiment, and maackiain glucuronidation/sulfation metabolism studies. The applications revealed that this method can be used for maackiain, M-7-S, and M-7-G analysis in both bioequivalent buffer and in blood.
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