Tripterygium wilfordii Hook. f. (Celastraceae) has been used in traditional Chinese medicine for more than 2 000 years. Worldwide
interest arose from reports on the antifertility effects of an extract from the plant on male rats as well as in men taking it to treat their rheumatoid arthritis and an international effort aimed at the bioassay-directed sub-fractionation of materials extracted from the plant was organized. To date, more than 400 samples (compounds/components) have been assayed and a series of 6 active male antifertility diterpene epoxides were isolated with their structure identified: T4 (tripchlorolide),T9 (triptolidenol), T13 (triptolide), T15 (tripdiolide), T7/T19(structure unpublished) and L2 (16-hydroxytriptohde). Among them T4 and L2 are new substances. When given orally for 7～8 weeks to male SD rats, the ED95 daily doses for T4,T7/T19,T9,T13 and T15 were 50, 400,100, 30 and 25 μg/kg, respectively. The results were similar :the fertility dropped to 0～10% of the control,and first the motility and then the concentration of spermatozoa in the cauda epididgmis were dramaticallg decreased. No discermible changes were seen in the testis and the histology of important somatic organs was unaltered. Their main target cells appeared to be epididymal spermatozoa and metamorphosing spermatids. It was shown that all these compounds suppressed the immune function when large doses were employed. Immuno-suppression is an important weakness for an antifertility agent, however,if the immuno-suppressive dose of a drug is much higher than its fertility-suppression dose,it could yet be regarded as a safe antifertility agent. Recently it was found that the immuno-suppressive effect of T7/T19 was much less than those of the other compounds. It is concluded that compunds isolated from T. wilfordii represent a new lead in the search for male antifertility agents,but their future will depend upon the results of meticulous safety evaluation.