Erm, from wikipedia:
The plant contains many active compounds, at least six of which have male anti-fertility effect (triptolide, tripdiolide, triptolidenol, tripchlorolide, 16-hydroxytriplide and a compound known as T7/19, whose structure is unpublished). The mechanism by which they affect fertility is not yet understood. What is known is that daily doses of these compounds reduce sperm counts and also severely affect the formation and maturation of sperm, causing them to be immotile.
On the other hand it seems to be effective against rheumatoid arthritis and pancreatic cancer. Not exactly a cure-all, though.