Simultaneous determination of linarin, naringenin and formononetin in rat plasma by LC‐MS/MS and its application to a pharmacokinetic study after oral administration of Bushen Guchi Pill

A sensitive and reproducible liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous determination of linarin, naringenin and formononetin in rat plasma after addition of sulfamethoxazole as the internal standard (IS). Separation was carried out on a Diamonsil C18 column (150 × 4.6 mm, 5 µm) with liner gradient elution using methanol (A) and 0.5‰ formic acid aqueous solution (B). Detection was performed on a triple-quadrupole linear ion trap mass spectrometer with the negative ion electrospray ionization in multiple-reaction monitoring (MRM) mode. The MRM transitions were m/z 591.2 → 283.2, 271.0 → 150.9, 266.9 → 252.0 and 252.0 → 155.9 for linarin, naringenin, formononetin and IS, respectively. All analytes showed good linearity within the concentration range (r > 0.9973). The lower limits of quantitation of linarin, naringenin and formononetin were 0.64, 1.07 and 1.04 ng/mL, respectively. Intra-day and inter-day precisions of the investigated components exhibited an RSD within 9.96%, and the accuracy (relative error) ranged from -11.25 to 9.38% at all quality control levels. The developed method was successfully applied to a pharmacokinetic study of linarin, naringenin and formononetin in rats after oral administration of Bushen Guchi Pill.