Bioactivity-guided Isolation of antiosteoporotic compounds from Ligustrum lucidum

The fruits of Ligustrum lucidum (FLL) has long been used for the treatment of osteoporosis in China, but the antiosteoporotic compounds in FLL are still poorly understood. In this study, the alkaline phosphatase (ALP) activity-guided isolation of osteogenic components from FLL was carried out by using osteoblast-like UMR-106 cells. Eight compounds, namely tyrosol (1), tyrosyl acetate (2), hydroxytyrosol (3), salidroside (4), oleoside dimethyl ester (5), oleoside-7-ethyl-11-methyl ester (6), nuzhenide (7), and G13 (8), were isolated and identified. Further study showed that compounds 3, 4, 7, and 8 increased ALP activity in UMR-106 cells. Compounds 5, 6, and 7 promoted the proliferation of UMR-106 cells. The aqueous extract of FLL-activated ERα/β-mediated gene transcription, whereas the isolated compounds were inactive. All eight isolated compounds also exhibited antioxidative activity, with compounds 1, 2, and 3 being the most potent. These results indicate that the antiosteoporotic effect of FLL is derived from different compounds together with different mechanisms such as ER-dependent or independent pathways and antioxidative effects. Salidroside (4) and nuzhenide (7) warrant further investigation as new pharmaceutical tools for the prevention and treatment of osteoporosis.