Beneficial Effects of a Flavonoid Fraction of Herba Epimedii on Bone Metabolism in Ovariectomized Rats

A flavonoid fraction of Herba Epimedii, including eight flavonoid glycoside compounds, epimedoside A, ikarisoside F, baohuoside II, sagittatoside A, sagittatoside B, 7-O-rhamnosyl icariside II, 2''-O-rhamnosyl icariside II, and baohuoside I, was isolated and prepared from the leaves of Herba Epimedii. This study was conducted to assess the potential effect of the flavonoid fraction of Herba Epimedii on osteoporosis in ovariectomized rats. Rats received repeated administration of a vehicle (ovariectomized), the flavonoid fraction of Herba Epimedii (7.5, 15, 30 mg/kg/d), and ipriflavone (200 mg/kg/d) once a day for 8 weeks, beginning 4 weeks after ovariectomization. Then, the bone turnover markers, bone biomechanical properties, trabecular architecture, and related protein expressions were evaluated by biochemical assay kits, mechanical testing, microcomputed tomography, immunohistochemical evaluation, and Western blot analysis. Treatment with the flavonoid fraction of Herba Epimedii (15, 30mg/kg/d) and ipriflavone (200 mg/kg/d) significantly increased bone strength while dramatically inhibiting the serum alkaline phosphatase and tartrate-resistant acid phosphatase levels in ovariectomized rats. Furthermore, the flavonoid fraction of Herba Epimedii also increased osteoprotegerin protein expression and reduced the receptor activator of nuclear factor-kappa B ligand protein expression compared with ovariectomized rats. In addition, the microcomputed tomography results showed that the flavonoid fraction of Herba Epimedii treatment significantly improved trabecular bone mineral density and restored the bone microarchitecture in ovariectomized rats. Therefore, our results indicated that the flavonoid fraction of Herba Epimedii might be beneficial for improving postmenopausal osteoporosis and should be considered as a promising candidate for treating postmenopausal osteoporosis.