[Determination of triptolide in tripterygium preparations by gradient high performance liquid chromatography]

A gradient elution method was developed for the separation and determination of triptolide in Tripterygium wilfordii Hook preparations by high performance liquid chromatography (HPLC) using YWG column made in China. Methanol with 0.05 mol/L KH2PO4 was used as mobile phase, and the photodiode array detector was used at lambda = 218 nm. The sample of tripterygium oral preparation was extracted with ethanol and then by chloroform. The extract solution was evaporated and the residue was dissolved in 10 mL of ethanol as a sample solution. The spectrum was obtained by the subtraction of spectrum of ethanol from that of sample solution. In comparing with isocratic elution, the gradient operation used in this paper had higher resolution and sensitivity. The calibration curve was linear over the range of 1.32-21.10 mg/L (r = 0.9999). The average recovery of the method was 97.59%. The method was applied to separate and determine the triptolide in tripterygium tablets and the results indicated that the triptolide content by this method was less than that by isocratic and label-claimed one.