Green Trapping of Zinc Ions in Solution by Flos Sophorae Immaturus Extract and Bi-Directional Selective Loading on Bio-Based Films for Functionalized Potentiation

Abstract

Expanding the scope and application value of natural extracts is a crucial strategy for promoting the sustainable use of economic and natural resources. Addressing this goal, Flos Sophorae Immaturus extract (SFE), obtained via DES solvent, was employed in this study as a natural trap, effectively capturing Zn2+ from the solution to obtain SFE-Zn metal complexes. The re-extraction ability of the recycled DES solvent was displayed with an effective extraction rate of up to 86.47% of the original extraction rate. As expected, the SFE-Zn exhibited excellent synergy effects and were validated by a high ABTS radical scavenging rate of 96% and minimal inhibitory/bactericidal concentrations of 1.25 mg/mL against S. aureus and E. coli. Subsequently. The bi-directional selection between the dynamically rearrangeable 3D hydrogen-bonding network based on the gelatin/chitosan matrix and the SFE-Zn effectively solved the problems of low accessibility and bioavailability due to their hydrophobicity. The successful loading of the SFE-Zn endowed the water solubility reduced to 24.15% and the tensile strength increased from 35.02 MPa to 47.33 MPa of the composite film. More surprisingly, at a 12% SFE-Zn loading, the composite film demonstrated 100% UV shielding, DPPH and ABTS radical scavenging rates of 94.82% and 99.05%, antimicrobial efficiencies of 99.80% (S. aureus) and 98.52% (E. coli), and nontoxicity. Moreover, preservation tests on fresh-cut apples and strawberries demonstrated significantly reduced weight loss and decay rates treated with GC/SZ-5 composite film solution, highlighting the film’s potential for food preservation applications.

Keywords: flavonoids, metal complexation, dynamic rearrangement, hydrogen bonding network, composite films