A pharmaceutical composition having a cytotoxic effect to a cancer cell and a method for the same are provided. The pharmaceutical composition comprises a flavonoid compound having at least one of the following formulas: and wherein B ring is a 4-oxo-cyclohexa-2,5-dienyl group, and any one of R 1- R 12 is one selected from a group consisting of hydrogen group, hydroxyl group, C1-C20 alkyl group, C1-C20 ether group, C1-C20 ester group, carboxyl group, halogen and sugar.