[Show abstract][Hide abstract] ABSTRACT: Tumor angiogenesis is a critical step for the growth and metastasis of solid tumors. Vascular endothelial growth factor (VEGF) is the most important angiogenic molecule associated with tumor-induced neovascularization. VEGF exerts its activity through binding to its receptor tyrosine kinase, KDR/Flk-1, expressed on the surface of endothelial cells. From the screening of medicinal plants, we have identified 1,2,3,4,6-penta-O-galloyl-beta-d-glucose (PGG) from the roots of Paeonia lactiflora that inhibited the binding of VEGF to KDR/Flk-1. PGG efficiently blocked VEGF-induced human umbilical vein endothelial cell proliferation and the growth of immortalized human microvascular endothelial cells, but did not affect the growth of HT1080 human fibrosarcoma and DU-145 human prostate carcinoma cells. PGG also blocked VEGF-induced capillary-like tube formation of endothelial cell on Matrigel. Our results suggest that PGG could be a candidate for developing anti-angiogenic agent.