Isolation and characterization of novel Iron-binding peptides from rapeseed protein hydrolysates: Structural analysis...

The Fe²⁺-chelating capacity of rapeseed protein (RP) hydrolysates from single-enzyme hydrolysis was evaluated using the o-phenanthroline method. Among six enzymes, Protease M at 180 min showed the highest chelation. Hydrolysates were purified via ultrafiltration, ion exchange, and gel filtration, yielding two peptides, DWK (Asp-Trp-Lys) and FLDLL (Phe-Leu-Asp-Leu-Leu), identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). These peptides exhibited Fe²⁺-chelating capacities of 246.56 ± 3.19 mg/g and 244.26 ± 4.78 mg/g. Structural analyses, including scanning electron microscopy, Fourier-transform infrared spectroscopy, particle size analysis, thermogravimetric analysis, and molecular modeling, revealed that residues such as Asp, Lys, and Leu form a stable octahedral complex with Fe²⁺ via carboxyl groups and water-mediated coordination. Chelation was mainly driven by electrostatic and coordination interactions, inducing peptide chain rearrangement and enhancing structural compactness and thermal stability. These findings clarify the chelation mechanism of RP-derived peptides and support DWK and FLDLL as efficient plant-derived iron supplements for functional foods and nutraceuticals.