Stimulatory activity of lignans from Machilus thunbergii on osteoblast differentiation

Phytoestrogens are naturally occurring compounds exerting estrogenic activity, and include isoflavonoids, flavonoids and lignans. In the present study, we evaluated the stimulating activity of six lignans, meso-dihydroguaiaretic acid, nordihydroguaiaretic acid, machilin A, guaiacin, isoguaiacin and isoguaiacin dimethylether, from Machilus thunbergii, on osteoblast differentiation employing primary cultures of mouse osteoblast as an in vitro assay system. Among the six lignans tested, arylnaphthalene type lignans such as guaiacin, isoguaiacin and isoguaiacin dimethylether significantly increased alkaline phosphatase activity, whereas bibenzylbutane type lignans such as meso-dihydroguaiaretic acid, nordihydroguaiaretic acid and machilin A showed little effects. Isoguaiacin and isoguaiacin dimethylether also increased collagen synthesis as well as calcium deposition. In addition, treatment of the mouse osteoblasts with tamoxifen markedly reduced ALP activity increased by isoguaiacin or isoguaiacin dimethylether, suggesting the involvement of estrogen receptor in the action of these lignans on osteoblast differentiation. Taken together, these results suggest that arylnaphthalene type lignans such as guaiacin, isoguaiacin and isoguaiacin dimethylether significantly increase osteoblast differentiation.