Orthosiphol A and B, novel diterpenoid inhibitors of TPA (12-O-tetradecanoylphorbol-13-acetate)-induced inflammation, from Orthosiphon stamineus

Two novel highly oxygenated pimarane diterpenes, orthosiphol A (1) and B (2), have been isolated from the dry leaves of Orthosiphon stamineus Benth (Labiatae). Their structures were elucidated by spectroscopic and chemical methods. Orthosiphol A and B showed potent inhibitory activity against the inflammation induced by a tumor promoter, TPA (12-O-tetradecanoylphorbol-13-acetate), on mouse ears