A comparative study on the effect of promoting the osteogenic function of osteoblasts using isoflavones from Radix Astragalus.

Abstract

Radix Astragalus has been shown to exert beneficial effects regarding the prevention postmenopausal osteoporosis. However, its mechanism of action remains to be investigated. Calycosin, formononetin, and calycosin-7-O-β-d-glucoside are the main isoflavone constituents of Astragalus. In this study, the abilities of these 3 compounds to promote osteogenic function of osteoblasts were compared, and the structure-activity relationships of these osteotrophic isoflavones were determined. Calycosin exhibited a greater effect than formononetin and calycosin-7-O-β-d-glucoside regarding improvements in osteogenic function of osteoblasts, as demonstrated by cell proliferation, alkaline phosphatase activity, collagen I and osteocalcin secretion, and the number and area of mineralized bone nodules. This suggests that calycosin may be better than formononetin and calycosin-7-O-β-d-glucoside at preserving bone mass. In addition, calycosin, formononetin, and calycosin-7-O-β-d-glucoside stimulate the expression of bone morphogenetic protein 2 and runt-related transcription factor 2 proteins, which indicates that all 3 agents may promote the osteogenesis of osteoblasts via regulation of bone morphogenetic protein 2 expression. In conclusion, calycosin may be the best candidate, with higher osteogenic activity than formononetin and calycosin-7-O-β-d-glucoside. The higher osteogenic activity of calycosin could be attributable to the superiority of its chemical structure (a hydroxyl group at position C3 of Ring B and no glucosyl group).