Inhibitory effect of fractions from skullcap (Scutellaria baicalensis Georgi) on osteoclast differentiation and bone resorption

This study was performed to evaluate the effects of skullcap (Scutellaria baicalensis Georgi, SBG) on differentiation of RAW 264.7 cell into osteoclast-like cells and bone resorption of mature osteoclast to propose candidates for the prevention or treatment of osteoporosis. In the screening of 140 natural products, the selected SBG methanol extract dramatically reduced tartrate-resistant acid phosphatase (TRAP) activity to 21% at 10 μg/mL. The proliferation was evaluated using the MTT assay, and the survival rates of RAW 264.7 cells treated with 10–100 μg/mL extract were over 80% with most concentrations. The chloroform fraction from SBG (SBG-C) decreased TRAP activity. The SBG-C increased the expression of the pro-apoptotic protein Bax and reduced the expression of the anti-apoptotic protein Bcl-2. It also stimulated caspase-3 activity in osteoclasts. In addition, the actin rings were loose and fuzzy in the presence of these fractions. A resorption pit was formed by multinucleated osteoclastic cells, but was not observed in the presence of the SBG-C (10 μg/mL). In conclusion, we found SBG suppressed osteoclast differentiation and bone resorption. It also inhibited osteoclast survival. Therefore SBG is expected to be a natural source for the development of functional food and medical agents to prevent or treat osteoporosis.