Six new furostanol saponins (1-6), named fistulosaponins A-F, three known furostanol saponins (7-9), and seven known aromatic compounds were isolated from seeds of Welsh onion (Allium fistulosum). The structures of these compounds were characterized by spectroscopic analyses including 2D NMR spectroscopy, mass spectrometry, and acid hydrolysis. The protective effect of the saponins on hypoxia-induced human umbilical vein endothelial cell injury was evaluated.