A comprehensive study on the bioactive flavonoids in Paulownia flowers: Uncovering metabolic pathways, effective components, and regulatory genes for industrial applications

Abstract

The study explores Paulownia flowers as an emerging resource in medicine, food, health supplements, cosmetics, and animal feed, despite a lack of characterization of their secondary metabolite accumulation mechanisms. We conducted a comprehensive investigation into the biological activities, metabolite profiles, and gene expression patterns of flavonoids in Paulownia flowers. Our results, obtained using ABTS/FRAP/DPPH assays, MTT assays, and colorimetric analyses, demonstrate the potent antioxidant, antibacterial, hypolipidemic, and antiproliferative activities of Paulownia flower flavonoid (PFF) extracts. Notably, the Paulownia elongata tetraploid (M4) exhibited particularly notable effects. HPLC fingerprinting, molecular docking, and density functional theory calculations led to the identification of rhoifolin and luteolin as key bioactive flavonoids. UV-Vis, fluorescence, and circular dichroism spectroscopy confirmed PFF's role as a reversible and mixed inhibitor of xanthine oxidase (XOD). Transcriptome and metabolomic analyses further revealed substantial enrichment in phenylpropanoid, flavonol, and flavonoid biosynthetic pathways, with PfPP2C, PfPYR, PfPYL, PfNPR1, PfMYBs, and PfbHLHs identified as crucial regulators. This work provides a foundational understanding of flavonoid biosynthesis in Paulownia flowers, paving the way for targeted genetic modification and biotechnological interventions aimed at enhancing flavonoid accumulation for industrial applications.