Determination of asperosaponin VI and its active metabolite hederagenin in rat tissues by LC-MS/MS: application to a tissue distribution study.

Two high-performance liquid chromatography (HPLC) coupled with electrospray ionization (ESI) mass spectrometry methods were developed and validated for the simultaneous determination of asperosaponin VI (A-VI) and hederagenin (HG) in rats' various tissues. Biological samples were processed with methanol extraction, and glycyrrhetinic acid was chosen as the internal standard (IS). The analytes were separated on a C18 column with two gradient elution programs for different rat tissue samples. The MS/MS detection was carried out by monitoring the transitions of m/z [MH](-) 927.5→603.4 for A-VI, m/z [MH](-) 471.3→471.3 for HG and m/z [MH](-) 469.4→425.4 for the IS, respectively. The lower limits of quantification (LLOQ) for the two analytes in different rat tissues were 2-6ng/mL, respectively. The methods were successfully applied to a tissue distribution study of A-VI and its active metabolite HG in rats. The results of the tissue distribution study showed that the highest concentration of A-VI was in the gastrointestinal (GI) tract. Besides, A-VI was mainly distributed in lung, liver, fat and ovary. HG was almost undetectable in most tissues except for the GI tract.