IN-VITRO ANTIALLERGIC ACTIVITY OF FLAVONOIDS IN HISTAMINE-RELEASE ASSAY USING RAT BASOPHILIC LEUKEMIA (RBL-2H3) CELLS

We used an established cell line, rat basophilic leukemia cells (RBL-2 H3) to screen 40 flavonoids for inhibitory activity on antigen-induced histamine release from immunoglobin E (IgE)-sensitized RBL-2H3 cells. To exclude non-specific inhibition, the cytotoxicity to RBL-2H3 cells was simultaneously determined. Flavonoid aglycones showed a stronger activity for histamine release-inhibition and cytotoxicity than glycos ides, and both activities were almost in parallel. Baicalein showed hi stamine release-inhibitory activity with the IC50 of 1.07 x 10(-5) M i n this bioassay system. However, it showed a potent cytotoxicity (IC50 9.62 x 10(-6) M). On the other hand, scutellarein (4'-hydroxybaicalei n) showed a potent histamine release-inhibitory activity (IC50 3.15 x 10(-6) M) and low cytotoxicity (IC50 6.11 x 10(-5) M). We found that s cutellarein has a potent histamine release-inhibitory activity and low cytotoxicity.