Antagonism of saikosaponin-induced prostaglandin E2 release by baicalein in C6 rat glioma cells.

There are several Kampo medicines (Chinese herbal medicines) containing both Bupleuri Radix and Scutellariae Radix, which are used for the treatment of inflammation. Saikosaponins are derived from Bupleuri Radix, and baicalein is from Scutellariae Radix. The present study was undertaken to investigate the pharmacological interaction of saikosaponin b1 and baicalein in prostaglandin E2 (PGE2) release from C6 rat glioma cells in vitro. Saikosaponin a, b1 and d potently stimulated PGE2 release, while saikosaponin b2 and c moderately stimulated PGE2 release. Saikosaponin b1 caused an irreversible elevation of intracellular Ca2+ concentration, which was eliminated by removing extracellular Ca2+. On the other hand, baicalein inhibited saikosaponin b1-induced PGE2 release in a concentration-dependent manner. These results suggest that saikosaponins are activators of PGE2 release, and baicalein is one of the functional inhibitors of PGE2 release by saikosaponins.