Xanthatin is isolated from?Xanthium strumarium?leaves. Xanthatin exhibits strong antitumor activities against a variety of cancer cells through apoptosis?persuasion?and shows anti-inflammatory activities by inhibiting?PGE2?synthesis and?5-lipoxygenase?activity. Xanthatin is a potent and orally active inhibitor of VEGFR2 kinase activity with an IC50 of 3.8 μM and prominently blocks the phosphorylation of VEGFR2 at Tyr951 site. Xanthatin inhibits angiogenesis and has the potential for the investigation of breast cancer.