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 μg/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 μg/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 μg/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 μg/mL.