Determination and pharmacokinetics of DT-13 in rat plasma by LC-MS.

A sensitive and specific LC-MS assay for DT-13 in rat plasma was developed. DT-13 is an active steroidal saponin present in Liriopes Radix and is developed as an anti-tumor drug candidate. The samples were extracted by acetonitrile-mediated plasma protein precipitation. The chromatographic separation was carried out using a Ultimate C(18) column (250 mm × 4.6 mm, i.d., 5 µm) with a mobile phase composed of acetonitrile: 5 mmol/L aqueous ammonium acetate (60:40, v:v). The method was validated and the specificity, linearity (r(2)=0.9980 within 10-1000 ng/mL), lower limit of quantitation (LLOQ, 10 ng/mL), precision (intra- and inter-day <12.3%), accuracy (93.4-106.3%), recovery (91.0 ± 4.7%) and stability were determined. The method was applied to the pharmacokinetic study of DT-13 in rat plasma after intravenous and intragastric administration. The results showed DT-13 underwent a prolonged absorption and slow elimination with a low oral bioavailability (5.51%) in rats.