A capsule containing the steroidal saponin ginsenoside Rg3 isolated from the root of Panax ginseng, with potential cancer preventive and anti-angiogenic activities. Upon oral administration, ginsenoside Rg3 appears to inhibit endothelial cell proliferation, migration and tubular formation, and promotes cancer cell apoptosis. This agent also modulates the activities of certain growth factors, such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and matrix metalloproteinases (MMPs), on tumor angiogenesis. In addition, ginsenoside Rg3 may be able to sensitize cancer cells to some chemotherapeutic agents.