Inhibitors of bone resorption from Halenia corniculata

Eleven xanthones (1-11), three flavonoids (12-14) and three secoiridoids (15-17) were isolated from the aerial parts of Halenia corniculata. Among those compounds, 1-hydroxy-2,3,4,5-tetramethoxyxanthone (1), 1-hydroxy-2,3,4,7-tetramethoxyxanthone (2), 1-hydroxy-2,3,4,5,7-pentamethoxyxanthone (3), 1-hydroxy-2,3,5-trimethoxyxanthone (4), 1,8-dihydroxy-3,5-dimethoxyxanthone (7), and luteolin (12), at the concentration of 1 microg/mL, effectively inhibited the osteoclast differentiation in a co-culture system with mouse osteoblastic calvarial cells and bone marrow cells. Notably, compounds 1, 3, and 4 exhibited, in a dose-dependent manner, significant inhibition of osteoclast differentiation even at a low concentration (0.01 microg/mL). All the inhibitory compounds, except for compound 7, significantly reduced the pit formation on the dentine slice compared with the control group. For the survival of the mature osteoclasts, compounds 1-4 and 12 (1 microg/mL), significantly decreased the survival number through induction of cell apoptosis, and compound 4 exhibited a significant inhibitory effect on osteoclast survival even at the low concentration of 0.1 microg/mL.