Biol. Pharm. Bull. 29(7) 1483—1486 (2006)

nial twining vine, grows densely on the shaded hill slopes in southern China. The extracts of the roots of the plant have been used in traditional Chinese medicine (named Lei-gongteng in Chinese) for the treatment of autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosus, and skin diseases for many years. A number of diterpenoids and triterpenoids have been isolated from Tripterygium wilfordii, some of them showed significant biological activities. For example, triptolide, wilforlide A, and triptonide (Fig. 1) have potent antitumor, anti-inflammatory, immunosuppressive, and anti-fertility activities. However, most of the terpenoids in Tripterygium wilfordii have a narrow therapeutic index and some serious side effects. Therefore, accurate measurement of these terpenoids in blood samples is essential from a safety point of view. Previous quantitative evaluations of these terpenoids have focused on triptolide in Tripterygium wilfordii and its ethyl acetate extracts. Analytical methods involved UV spectrophotometry, thin layer chromatography, HPLC with UV detection, and capillary electrophoresis. Most of them, however, were developed for quantitative determination of triptolide in plants or medical preparations. There were fewer methods reported to be used in biological fluids. Yang et al. developed a gas chromatography (GC) method for the determination of triptolide in human plasma. Wang et al. developed an HPLC method for the determination of triptolide and triptonide in human plasma. Although the published GC method was sensitive (LLOQ: 1 ng/ml), it required derivatization for triptolide with trifluoroacetic anhydride and required laborious sample pretreatment, therefore it was not convenient for analysis of large numbers of samples. The HPLC method was not sensitive enough (LLOQ: 10 ng/ml) to support the pharmacokinetic and toxicokinetic studies. Furthermore, the two methods needed a tediously long analysis time. The aim of this study is to develop a simple and selective high-performance liquid chromatography-electrospray ionization mass spectrometry (LCESI-MS) method for the determination of triptolide, wilforlide A and triptonide in human plasma.