Triptolide is a diterpene triepoxide, immunosuppresive agent extracted from the Chinese herb Tripterygium wilfordii.

Triptolide is the major bioactive constituent of T. wilfordii Hook F., also known as the Thunder God Vine, a traditional Chinese medicinal herb with known antiproliferative, immunosuppressive, anti-inflammatory, antifertility, and antipolycystic kidney disease effects. Triptolide binds to and inhibits human dCTP pyrophosphatase 1, a “gatekeeper” enzyme that prevents deleterious halogenated nucleotides from entering DNA synthesis, with a Ki value of 168 μM and an IC50 value of 7-10 nM.Triptolide has also been shown to inhibit LPS-stimulated induction of cyclooxygenase 2 mRNA and synthesis of prostaglandin E2 in human peripheral blood monocytes, rheumatoid arthritis synovial fibroblasts, and human neonatal foreskin fibroblasts with an IC50 value of 0.04 μM.