A bandiflavone from baby corn silk ( Zea mays L.): structural elucidation, radical-scavenging activity, and HPLC quantification

Corn silk (Zea mays L.), a global agricultural byproduct, is rich in bioactive compounds. This study characterised antioxidant flavones from a new baby corn silk (BCS) variety, Bandiburichodang. Three flavones were isolated: bandiflavone (1), a previously unreported natural product, along with demethyltorosaflavone C (2) and D (3). Spectroscopic analysis established the structure of compound 1 as a unique luteolin derivative featuring an α,β-unsaturated δ-lactone moiety fused to the A-ring. All compounds exhibited significant radical-scavenging activity; notably, compound 1 showed potent effects with IC50 values of 0.97 mM (DPPH•) and 0.29 mM (ABTS•+), which were comparable to or stronger than those of L-ascorbic acid (0.84 and 0.73 mM, respectively). Quantification via HPLC indicated that the concentrations of compounds 1–3 within the BCS extract reached 3.09, 0.91, and 3.97 mg/g, respectively. These findings expand the phytochemical profile of BCS and highlight its potential as a high-value source for functional food ingredients or dietary supplements.