As a commonly used traditional Chinese medicine, Flemingia macrophylla is rich in isoflavones and has potential therapeutic effects on osteoporosis. However, there is little research and development on it as a health food ingredient targeting the prevention of osteoporosis in China.

This experiment investigates the effect and potential mechanism of a new health food containing Flemingia macrophylla on the improvement of osteoporosis.

According to the limit test protocol in the National food Safety Standard-Acute Oral Toxicity Test, an acute oral toxicity test of Flemingia macrophylla mixed powder was designed. An osteoporosis model was established through ovariectomy in 32 SPF adult female infertile SD rats which were randomly divided into one sham operation group and three model groups (one model control group, and one model+Flemingia macrophylla mixed powder group, and one model+flour mixed powder group) after stratification according to body weight. The model control group was given water, and the other two model groups were given powder by oral administration at 10 mL·kg^-1 (in body weight) every day for 13 weeks. At the end of the experiment, the femoral bone mineral density, femoral dry weight, and bone calcium content were measured, and the pathological changes of femur and the thickness of bone cortex were detected. The effects of Flemingia macrophylla extract on the proliferation and differentiation of neonatal rat calvarial osteoblasts were investigaed in vitro: The Flemingia macrophylla was extracted by ultrasound and purified with AB- 8 macroporous adsorption resins to obtain different methanol eluates; at the optimal methanol concentration, the osteoblasts were treated with Flemingia macrophylla extract (0.2, 0.4, 0.6, 0.8, and 1.0 g·L^-1 respectively), icariin (0.4 g·L^-1, positive control group), and DMSO (0.1%, solvent control group) for 24, 48, and 72 h, respectively; the proliferation and alkaline phosphatase (ALP) expression of osteoblasts were determined with CCK-8 and ALP kits respectively.

The acute oral toxicity test results showed that the tested Flemingia macrophylla mixed powder belonged to the actual nontoxic grade. After 13 weeks of the designed intervention, compared with the model control group, the bone mineral density and the bone cortex thickness in the Flemingia macrophylla mixed powder group and the flour mixed powder group were significantly higher (P < 0.05); furthermore, compared with the flour mixed powder group(302.87±64.83) μm, the bone cortex thickness in the Flemingia macrophylla mixed powder group(376.01±51.52) μm increased (P < 0.05). The results of pathological examination showed that compared with the model control group, the number of bone trabeculae in the Flemingia macrophylla mixed powder group increased significantly, the degree of separation decreased, and the trabecular structure became tighter; in addition, the above indicators of the Flemingia macrophylla mixed powder group were significantly better than those of the flour mixed powder group. According to the ALP activity and total flavonoids of osteoblasts at different methanol gradients, 60% methanol was determined to be the optimal elution gradient. Under the optimized gradient, the results of CCK-8 and ALP activity assay showed that compared with the solvent control group, the Flemingia macrophylla extract at different concentrations inhibited the proliferation of osteoblasts and increased the activity of ALP after 24 h, 48 h, and 72 h, respectively (P < 0.05).

The health food product containing Flemingia macrophylla could improve bone function in rats, and its mechanism may be related to promoting the differentiation of osteoblasts.