Ultrasound-assisted extraction and macroporous resin purification of bioactive polyphenols from Paulownia flower

This study developed an integrated extraction-purification system for bioactive polyphenols from Paulownia tomentosa flowers using green technologies. Through response surface methodology, optimal ethanol extraction conditions were established (90 % ethanol, 1:15 ratio, 240 W/20 min ultrasonication), yielding 0.136 mg/g polyphenols, with HPD-722 resin purification achieving >85 % purity. The purified extract contained 32 identified compounds, with luteolin (0.46 μg/g) and apigenin (0.32 μg/g) as the major flavonoids, luteolin-7-O-glucuronide and apigenin-6-C-glucoside were tentatively characterized. Notably, the extract exhibited antiradical capacity (ABTS IC₅₀: 185.0 μg/mL), mixed-type inhibition of α-glucosidase/xanthine oxidase, and preferential binding to taurocholate. Concentration-dependent fluorescence quenching indicated the formation of polyphenol-enzyme complex, FT-IR analysis confirmed secondary structure perturbations in α-glucosidase. Molecular docking suggested polyphenol-enzyme interactions were primarily mediated by hydrogen bonding and hydrophobic forces. These findings collectively advance the understanding of Paulownia flower polyphenols (PFP) as multi-functional agents, providing a technically feasible process for their utilization in functional food and nutraceutical applications.