A study was carried out to clarify the active component of green fruit of Citrus unshiu MAKOVICH on the type I allergic reaction. The flavonoid component, isolated from its methanolic extract, hesperidin, was found to inhibit histamine release from peritoneal mast cells of rats induced by compound 48/80. Forty eight-hour homologous passive cutaneous anaphylaxis (PCA) in intact rats was significantly inhibited by the oral administration of hesperidin. However, the anti-allergic action on PCA was not observed in adrenalectomized rats. These results suggests that hesperidin is an effective component of the fruit of Citrus unshiu with the anti-allergic action against the type I reaction.
