Synthesis and antitumor activity of formononetin nitrogen mustard derivatives

► Sixteen novel formononetin nitrogen mustard derivatives were designed and synthesized. ► Their cytotoxic activities to human tumor in vitro have been screened. ► The pharmacological results showed that many of the new derivatives displayed more potent cytotoxicity than alkeran. ► Compounds 6d and 6n could induce cell cycle arrest at G2/M phase and cell apoptosis.