Flavan‐3‐ol isolated from rhizome of Drynaria fortunei (Kunze) J. Sm. exerts osteoprotective effects via its actions on osteoblastogenesis and osteoclastogenesis

(‐)‐Epiafzelechin (FRD) is a flavan‐3‐ol found in rhizome of Drynaria fortunei (Kunze) J. Sm., a Chinese herb commonly used for management of bone diseases. Previous study suggested FRD could stimulate osteoblastic functions. Our study aims to determine if FRD act on osteoblastogenesis and osteoclastogenesis, and if its actions in bone cells involve the activation of Estrogen Receptors (ER) using pre‐osteoblast MC3T3‐E1, pre‐osteoclast RAW 264.7 as well as osteoblast‐like UMR 106 cells. FRD could increase alkaline phosphatase activity and secretory collagen in MC3T3‐E1 cells. FRD could reduce viability of RAW 264.7 cells and prevent the formation of osteoclastic cells, as observed by a reduction of Tartrate‐resistant acid phosphatase activity. Co‐incubation of ER antagonist (ICI 182780) with FRD abolished its positive effects on UMR 106 cell growth. FRD has a weak binding affinity to ER‐alpha and beta and could only weakly activate ER‐alpha, but not ER‐beta, mediated Estrogen Response Element (ERE)‐dependent transcriptional activity in UMR 106 cells. In conclusion, our results showed that FRD could stimulate osteoblastogenesis and inhibit osteoclastogenesis and its positive effects in bone cells appeared to be ER dependent. Funding support: RGC General Research Fund [POLYU 563209] and research studentship from the Hong Kong Polytechnic University