Anti-allergic components from the peels of Citrus unshiu

In a bioassay-guided search for anti-allergic compounds from higher plants of Korea, polymethoxyflavones, 3 ',4',5,6',7,8-hexamethoxyflavone (I), 5-hydroxy-3',4',6,7,8-pentamethoxyflavone (II) and 3',4',5,7,8,-pentamethoxyflavone (III) have been isolated from the immature peels of Citrus unshiu. Structures of these compounds were elucidated on the basis of spectroscopic techniques. Compounds I and II inhibited dose-dependently histamine release from the rat peritoneal mast cells activated by compound 48/80 or anti-DNP IgE.