AIM: To determine the effect of tetrahydrocurcumin (THC) on tumor angiogenesis compared with curcumin (CUR) by using both in vitro and in vivo models of human hepatocellular carcinoma cell line (HepG2). METHODS: The 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay was used for testing the anti-proliferating activities of CUR and THC. In male BALB/c nude mice, 2 × 106 human HepG2 cells were inoculated onto a dorsal skin-fold chamber. One day after HepG2 inoculation, the experimental groups were fed oral daily with CUR or THC (300 mg/kg or 3000 mg/kg). On d 7, 14 and 21, the tumor microvasculature was observed using fluorescence videomicroscopy and capillary vascularity (CV) was measured. RESULTS: Pathological angiogenic features including microvascular dilatation, tortuosity, and hyper-permeability were observed. CUR and THC could attenuate these pathologic features. In HepG2-groups, the CV were significantly increased on d 7 (52.43%), 14 (69.17%), and 21 (74.08%), as compared to controls (33.04%,P < 0.001). Treatment with CUR and THC resulted in significant decrease in the CV (P < 0.005 and P < 0.001, respectively). In particular, the anti-angiogenic effects of CUR and THC were dose-dependent manner. However, the beneficial effect of THC treatment than CUR was observed, in particular, from the 21 d CV (44.96% and 52.86%, P < 0.05). CONCLUSION: THC expressed its anti-angiogenesis without any cytotoxic activities to HepG2 cells even at the highest doses. It is suggested that anti-angiogenic properties of CUR and THC represent a common potential mechanism for their anti-cancer actions. AIM: To determine the effect of tetrahydrocurcumin (THC) on tumor angiogenesis compared with curcumin (CUR) by using both in vitro and in vivo models of human hepatocellular carcinoma cell line (HepG2). METHODS: The 3- (4,5-dimethylthiazol -2-yl) -2, 5-diphenyl-tetrazolium bromide (MTT) assay was used for testing the anti-proliferating activities of CUR and THC. In male BALB / c nude mice, 2 × 10 6 human HepG2 cells were inoculated onto a One day after HepG2 inoculation, the experimental groups were fed oral daily with CUR or THC (300 mg / kg or 3000 mg / kg). On d 7, 14 and 21, the tumor microvasculature was observed using fluorescence RESULTS: Pathological angiogenic features including microvascular dilatation, tortuosity, and hyper-permeability were observed. CUR and THC could attenuate these pathologic features. In HepG2-groups, the CVs were significantly increased on d7 (52.43%), 14 (69.17%), and 21 (74. Treatment with CUR and THC resulted in significant decrease in the CV (P <0.005 and P <0.001, respectively). In particular, the anti-angiogenic effects of However, the beneficial effect of THC treatment than CUR was observed, in particular, from the 21 d CV (44.96% and 52.86%, P <0.05). CONCLUSION: THC expressed its anti-angiogenesis without any cytotoxic activities to HepG2 cells even at the highest doses. It is suggested that anti-angiogenic properties of CUR and THC represent a common potential mechanism for their anti-cancer actions.