Simultaneous determination of active flavonoids and alkaloids of Tang-Min-Ling-Pill in rat plasma by liquid chromatography tandem mass spectrometry

A rapid, sensitive and reliable liquid chromatography tandem mass spectrometry (LC–MS/MS) method was developed and validated for simultaneous determination of five active flavonoids (wogonin, chrysin, oroxylin A, naringenin, hesperetin) and four major alkaloids (berberine, coptisine, jatrorrhizine, palmatine) from Tang-Min-Ling-Pill in rat plasma. Plasma samples (100 μL) were spiked with internal standards daidzein (for flavonoids) and tetrahydropalmatine (for alkaloids), acidified with HCl and extracted by liquid–liquid extraction with acetone. Chromatographic separation was performed on a Zorbax SB-C18 column with the mobile phase of water (containing 0.1% of formic acid)–acetonitrile (30:70, v/v) at a flow rate of 0.3 mL/min in a run time of 7.0 min. Detection was performed by multiple reaction monitoring mode using electrospray ionization in the positive ion mode. All analytes showed good linearity over the investigated concentration range (r > 0.9900). The validated lower limit of quantification was 1.01 ng/mL for wogonin and oroxylin A, 0.238 ng/mL for chrysin, 1.01 ng/mL for naringenin, 0.998 ng/mL for hesperetin, 0.0505 ng/mL for berberine, 0.0996 ng/mL for coptisine, 0.0501 ng/mL for jatrorrhizine, 0.0889 ng/mL for palmatine, respectively. Intra- and inter-day precision (RSD%) was less than 15% and accuracy (RE%) ranged from −7.5% to 4.5%. The validated method was successfully applied to investigate the pharmacokinetics of the major flavonoids and alkaloids of Tang-Min-Ling-Pill after oral administration to rats.