Inhibition of prostaglandin E2 production by platycodin D isolated from the root of Platycodon grandiflorum

Platycodin D, isolated from the root of Platycodon grandiflorum A. DC. (Campanulaceae) suppressed prostaglandin E-2 production at 10 and 30 muM in rat peritoneal macrophages stimulated by the protein kinase C activator 12-O-tetradecanoylphorbol 13-acetate (TPA). Platycodin D-3 and oleanolic acid showed no effect at these concentrations. Western blot analysis revealed that the induction of COX-2 protein by TPA was inhibited by platycodin D in parallel with the inhibition of prostaglandin E-2 production. Platycodin D showed no direct effect on COX-1 and COX-2 activities. TPA-induced release of [H-3]arachidonic acid from pre-labeled macrophages was also not inhibited by platycodin D.