Ononin Mitigates Estrogen Deficiency‐Induced Osteoporosis Through Activation of <scp>ALDH2</scp> in Mice

Postmenopausal osteoporosis (PMOP) results from estrogen deficiency, oxidative stress, and impaired bone formation, yet effective treatments remain limited. In this study, we identify the natural isoflavone ononin as a potent antiosteoporotic compound and uncover its mechanism through activation of aldehyde dehydrogenase 2 (ALDH2). Using an ovariectomized (OVX) mouse model and bone marrow-derived mesenchymal stem cells (BMSCs), we evaluated the in vivo and in vitro effects of ononin. An integrated approach combining network pharmacology, molecular docking, enzymatic assays, and ALDH2 knockout (Aldh2^-/-) models was employed to verify its molecular target. Ononin significantly alleviated OVX-induced trabecular bone loss and promoted osteogenic differentiation of BMSCs in a dose-dependent manner. Mechanistically, network pharmacology and docking analyses identified ALDH2 as the primary target. Enzymatic assays confirmed that ononin robustly enhances ALDH2 activity, reduces reactive oxygen species, lowers 4-hydroxynonenal and malondialdehyde levels, and maintains mitochondrial integrity. These beneficial effects were largely abolished in Aldh2^-/- mice, confirming the dependence on ALDH2 activation. Collectively, these findings demonstrate that ononin protects against PMOP by promoting ALDH2-mediated osteogenesis and restoring redox balance, highlighting its potential as a natural therapeutic agent for postmenopausal osteoporosis.