Abstract: AimTo determine the anti-angiogenic activity of emodin. MethodsChick embryo assay and cultured endothelial cells were used. ResultsEmodin at doses of 150 and 300 μg/egg caused 37.6% and 63.2% inhibition of angiogenesis, respectively. Emodin was shown to inhibit the proliferation of primary cultured bovine aortic endothelial cells in the absence or presence of basic-fibroblast growth factor (bFGF) or the presence of vascular endothelial growth factor (VEGF) in a dose-dependent manner. The IC₅₀ values by MTT assay were 5.56 , 8.40 or 6.91 mg·L^-1, respectively. Emodin at concentrations from 5.4 to 21.6 mg·L^-1 induced apoptosis of endothelial cells for 37.6% to 72.6%. Emodin caused endothelial cell cycle arrest at G₂/M phase. After emodin treatment, there was a down-regulation of Cyclin B1, P34^cdc2, and Bcl-2 protein expression while the Bax protein expression was unaffected. ConclusionEmodin shows anti-angiogenic activity and might be useful for the development of novel anti-cancer therapy.