Chitosan-modified magnetic particles for efficient extraction of flavonoids from Flos sophorae immaturus: Characterization, optimization and selective adsorption of catechol-containing structure

Efficient separation and purification of bioactive components from medicine-food homologous plants represent a key challenge in natural product development. To address the cumbersome, time-consuming, and costly drawbacks of traditional flavonoid extraction techniques, this study developed a novel ultrasound-assisted magnetic dispersive solid-phase extraction method (UA-MSPE). Chitosan-modified Fe₃O₄ magnetic composite microspheres (CS@Fe₃O₄CMs) were employed as functional adsorbents with 70 % methanol solution as the desorbent to achieve selective separation and enrichment of catechol-containing flavonoids from Flos sophorae immaturus (FSI). Systematic characterization by FT-IR, XRD, TGA, VSM confirmed successful fabrication of CS@Fe₃O₄CMs, which exhibited high magnetic responsiveness (saturation magnetization of 30.67 emu/g), thermal stability (total weight loss <10 % within 650 °C) and recyclability (retaining over 90 % of initial adsorption capacity after 3 cycles). Adsorption processes conformed to the Langmuir model (monolayer adsorption) and pseudo-second-order kinetics (chemisorption), with a yield of catechol-containing flavonoids reaching 147.06 ± 1.609 mg/g. The selective adsorption was primarily attributed to hydrogen bonding and π-type hydrogen bonding interactions between abundant amino and hydroxyl groups on the chitosan surface and catechol structures of flavonoids. This strategy provides a new green approach for separating catechol-containing flavonoids and expands the application of magnetic solid-phase extraction technology in food and pharmaceutical fields.