Pharmacokinetics of triptolide. Development and application of a high performance liquid chromatographic method for quantitation of triptolide in plasma

In order to evaluate the bioavailability and study the pharmacokinetics of triptolide, an HPLC method was developed for the quantitative determination of this diterpenoid in plasma. The procedure for the plasma assay employed liquid - liquid extraction with chloroform followed by high speed centrifu gation. The UV absorbance of the effluent was monitored at 218 nm. An inter nal standard (acetophenone) was used to calibrate injection and instrument reaction errors. The proposed methodology is sensitive, rapid, and reproduc ible. The limit of quantitation is 0.005 mg/L in plasma (0.05 mg /L in fina l solution) and a linear range of determination is observed over the concen tration of 0.05 mg/L to 30 mg/L. The inter- and intraday coefficients of va riation for the assay of triptolide in plasma were < 16.82% at low concentr ation (0.005-0.076 mg/L) and < 8.05% at high concentration (0.152-5.000 mg/ L). Recovery of triptolide in plasma is greater than 96.72%. Triptolide was stable in plasma during 30 days of storage at 80 degrees C, whereas degradation products appeared within 4 hours when it was dissolved in methanol at room temperature. The method was employed to determine the p harmacokinetics of triptolide in rat plasma. After oral administration of a single dose of 840 mu g/kg, triptolide was f ound to reach a peak concentration (Cmax) of 0.210 mu g/mL in 19.5 min. (Tm ax). The AUC was 157.28 mu g and the elimination half time was 50.60 min..