Forsythia viridissima Leaf Extract Inhibits Trabecular Bone Mineral Loss in Rats Induced by a Low-Calcium Diet

The Forsythia has been used in herbal medicine, and the leaf is also expected to contain various putative bioactive substances. In this study, we investigated the effects of Forsythia viridissima leaf extract (FLE) on bone metabolism. The anti-osteoporotic effect of FLE was determined in male rats fed a low-calcium diet. Micro-CT analysis of the distal end of the left femur showed a trend toward less reduction in total bone mineral density (total BMD) in the group received FLE on a 0.05% low-calcium diet compared to the low-calcium control group. Also, trabecular bone mineral density (Tb.BMD) was significantly less decreased in the FLE group. Then, in vitro experiment, we found that matairesinol, a lignan particularly rich in Forsythia leaf, remarkably promotes osteoblastic mineralization. Thus, our study revealed that FLE inhibits the progression of osteoporosis caused by calcium deficiency.