When the balance is broken due to various diseases, aging, smoking, stress, or sudden estrogen depletion of women, bone absorption is increased relative to bone formation, resulting in bone loss (6,7). Osteoporosis can easily cause fractures, even in the case of mild impacts, and the bone mass per unit volume decreases without significant changes in the chemical composition of the bone (8). Osteoclasts are differentiated and activated by the receptor activator of nuclear factor kappa-B ligand (RANKL) that is secreted by osteoblasts. Activated osteoclasts form an actin ring composed of a fibrous actin sequence between the cell membrane and bone matrix. They secrete proteases and protons, thereby absorbing bone matrix and reducing bone density (9). To inhibit bone resorption, studies are under way to inhibit the early stage of differentiation that blocks the conversion from osteoclast precursor cells to osteoclasts, or to induce the death of differentiated osteoclasts, thereby inhibiting the bone resorption process (10,11). Recently, there is growing concern about the relationship between oxidative stress and osteoporosis (12). In women with osteoporosis, blood concentrations of antioxidants are decreased (13), and bone Effects of pressurized steam-treated Corni Fructus extract on osteoblast differentiation and osteoclast formation