Pharmacokinetics and bioavailability of isotalatizidine in rat plasma by UPLC-MS/MS

Abstract Isotalatizidine, a key C19-diterpenoid alkaloid extracted from the lateral roots of Aconitum carmichaelii , is widely recognized for its therapeutic effects in pain relief, inflammation reduction, rheumatism treatment, and immune suppression. This study was centered on the development and validation of a UPLC-MS/MS technique for quantifying isotalatizidine concentrations in rat plasma, as well as investigating its pharmacokinetic characteristics. Midazolam served as the internal standard (IS), and plasma samples were processed through protein precipitation using acetonitrile. Chromatographic separation was carried out on a UPLC BEH C18 column with a mobile phase consisting of acetonitrile and 0.1% formic acid under gradient elution conditions. Detection was achieved via electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode with a positive ion interface, monitoring the transitions m / z 408.5→390.5 for isotalatizidine and m / z 326.2→291.4 for the IS. The calibration curve exhibited linearity within the concentration range of 1–576 ng mL −1 ( r > 0.995). Both intra-day and inter-day precision values remained below 8.7%. Accuracy fell within the range of 94.9%–109.0%, while matrix effects were observed between 101.5% and 108.6%. This validated method was effectively applied to assess the pharmacokinetics of isotalatizidine after both oral and intravenous administration in rats, indicating an absolute bioavailability of 5.9%.