Structurally diverse flavonoids from the seeds of Astragalus complanatus with ferroptosis regulation via the NOX4/Nrf2 axis in neural cells.

The seeds of Astragalus complanatus R. Br. (SAC), a medicinal food homologous resource, are widely distributed and utilized in China. A phytochemical investigation of the seeds of SAC afforded 47 flavonoids, including eight previously undescribed ones, designated as complanatin A (2), and neocomplanatosides A-G (38, 39, and 43-47). Among them, 43 and 44 are phenylpropanoid-esterified flavonoid glycosides, while 45-47 represent a rare class of sesquiterpene-esterified flavonoid glycosides. Their structures were elucidated by the NMR and HRESIMS spectroscopic data, and ECD calculations. Biological evaluation demonstrated that rhamnocitrin (15) inhibited ferroptosis in erastin-induced HT22 cells (EC50 = 7.79 ± 0.44 μM) by suppressing NOX4 expression and activating the SLC7A11/Nrf2 pathway. Molecular dynamics simulations confirmed its stable binding to NOX4 (RMSD <0.4 nm; ΔGbind = - 47.92 kJ/mol), and competitive inhibition with GLX351322 further confirmed NOX4 as the direct target. These findings indicate that flavonoids from SAC, particularly rhamnocitrin (15), are promising natural neuroprotective candidates for food-based health applications.