A series of (E)-5-alkoxy-3-(3-phenyl-3-oxoprop-1-enyl)-4H-chromen-4-ones (4) and (E)-5- alkoxy-3-(3-hydroxy-3-phenylprop-1-enyl)-4H-chromen-4-ones (5) were synthesized and evaluated for their IL-5 inhibitory activity. Propenone analogs 4 possess some of the structurally important characteristics of isoflavone 2 and chalcone 3 previously known as potent IL-5 inhibitor. However, the inhibitory activity of 4 was weak and therefore this ...