Abstract:A new diterpene bisepoxide, 12-epitriptriolide (L1) was isolated from the leaves and roots of Tripterygium wilfordii Hook f. and from the marketed drug "Total Glycoside of Tripterygium wilfordii". This compound was crystallized from CHC13 as colorless needles,mp 267.5-269.5 C. Its molecular formula is C20H26O7. The structure was identified on the basis of spectral data (IR, MS, UV,1H-NMR,13C NMR, 2D-NMR,13C-NOE, NOE difference spectroscopy and selective long-range DEPT NMR) analyses. 12-epitriptriolide was shown to have a potent anti-inflammatory action. Its effective dose was 40 mg/kg with the murine model of ear swelling induced by croton oil while that of triptriolide was 70 mg/kg . The results showed that the action of the structure in connection with 12-αOH was about 2 times stronger than that of 12-βOH. 12-epitriptriolide showed no immunosuppressive and antifertility (male) actions in mice and had low toxicity (LD50>250 mg/kg ) in experimental animals. The preliminary assay for the structure-activity relationship revealed that the epoxide group on C12.13 of diterpene from T. wilfordii was one of the key positions associated with immunosuppressive and antifertility actions and toxicioty.