Garcinone B reduces prostaglandin E₂ release and NF-κB-mediated transcription in C6 rat glioma cells

In the course of our survey of natural compounds inhibiting prostaglandin E₂ release and/or lipopolysaccharide (LPS)-induced transcriptional stimulation via NF-κB, a central regulator of inflammatory genes, from natural resources, we found garcinone B, a xanthone from callus tissue culture of Hypericum patulum, as a compound with such pharmacological activities, that is a derivative of γ-mangostin which potently inhibits COX-1 and COX-2 activities to reduce PGE₂ release from C6 rat glioma cells, and inhibits IKK activity to prevent NF-κB-dependent COX-2 gene transcription. Garcinone B, to a lesser extent, reduced A23187-induced increase in prostaglandin E₂ release than γ-mangostin and its structurally related compound, patulone, in C6 cells. This compound also prevented LPS-induced stimulation of NF-κB-dependent transcription. These results suggest that garcinone B becomes a unique pharmacological tool to investigate intracellular signaling pathways involved in inflammation.