Degranulation Inhibitors from Petals of Coreopsis grandiflora

The extracts of petals of Coreopsis grandiflora, a member of the Asteraceae family, were found to inhibit degranulation in RBL-2H3 cells, and lanceoletin, leptosidin, okanin, and 4-methoxylanceoletin were isolated as degranulation inhibitors by liquid-liquid separation and column chromatography. The intensities of the antigen-stimulated degranulation inhibitory activities of the four flavonoids were in the order of leptosidin, okanin, lanceoletin and 4-methoxylanceoletin. Leptosidin, which inhibited antigen-stimulated degranulation most greatly, inhibited calcium ionophore-stimulated degranulation with the same intensity as that of lanceoletin and okanin. As a result of investigation of the structure-activity relationships of the four isolated active compounds for antigen-stimulated degranulation inhibitory activities, it was found the inhibitory activity of lanceoletin, a chalcone, was enhanced by forming a C ring and becoming leptosidin, an aurone. In addition, the three chalcones tended to have greater degranulation inhibitory activity as their molecule polarities increased.