The Biflavonoid Amentoflavone Inhibits Neovascularization Preventing the Activity of Proangiogenic Vascular Endothelial Growth Factors*

The proangiogenic members of VEGF family and related receptors play a central role in the modulation of pathological angiogenesis. Recent insights indicate that, due to the strict biochemical and functional relationship between VEGFs and related receptors, the development of a new generation of agents able to target contemporarily more than one member of VEGFs might amplify the antiangiogenic response representing an advantage in term of therapeutic outcome. To identify molecules that are able to prevent the interaction of VEGFs with related receptors, we have screened small molecule collections consisting of >100 plant extracts. Here, we report the isolation and identification from an extract of the Malian plant Chrozophora senegalensis of the biflavonoid amentoflavone as an antiangiogenic bioactive molecule. Amentoflavone can to bind VEGFs preventing the interaction and phosphorylation of VEGF receptor 1 and 2 (VEGFR-1,VEGFR-2) and to inhibit endothelial cell migration and capillary-like tube formation induced by VEGF-A or placental growth factor 1 (PlGF-1) at low μm concentration. In vivo, amentoflavone is able to inhibit VEGF-A-induced chorioallantoic membrane neovascularization as well as tumor growth and associated neovascularization, as assessed in orthotropic melanoma and xenograft colon carcinoma models. In addition structural studies performed on the amentoflavone·PlGF-1 complex have provided evidence that this biflavonoid effectively interacts with the growth factor area crucial for VEGFR-1 receptor recognition. In conclusion, our results demonstrate that amentoflavone represents an interesting new antiangiogenic molecule that is able to prevent the activity of proangiogenic VEGF family members and that the biflavonoid structure is a new chemical scaffold to develop powerful new antiangiogenic molecules.