Structural alterations of wogonin were conducted to observe the role of each functional group at the A-ring of wogonin on the inhibitory activities against COX-2 catalyzed $PGE_2$ production from LPS-induced RAW 264.7 cells. Serial deletion of the functional groups at the A-ring of wogonin exhibited low to comparable bioactivity. The present study validated that all the functional groups at the A-ring of wogonin are important factors to exhibit the optimum inhibitory activities.