Iron-chelating activity of Andean Lupinus mutabilis Sweet protein and casein under the INFOGEST in vitro gastrointestinal model: peptide identification, molecular docking, and synthesis

Anemia primarily caused by dietary iron deficiency is considered a global public health problem. The local crop diversity may have potential as a source of novel iron delivery systems, such as iron-chelating peptides, which can be also generated during the intake of high-protein foods. This study evaluated for the first time the iron-chelating activity of the Andean Lupinus mutabilis Sweet protein in comparison with casein using the INFOGEST in vitro gastrointestinal digestion model. Depending on the type of protein, the variation of the soluble protein contents, the degree of hydrolysis (DH) and the iron-chelating activities along the gastric and intestinal phases followed different trends. Gastrointestinal L. mutabilis hydrolysates showed higher DH and iron-chelating activities than casein hydrolysates. Eleven peptides were identified in casein hydrolysates by LC-MS/MS and matched with those found in casein. In case of L. mutabilis protein hydrolysates, from the thirty-one peptides identified de novo , only five matched with the amino acid sequences found in α-2 conglutin and α-conglutin from L. angustifolius . The molecular docking analysis (evaluated in the five L. mutabilis and eleven casein peptides) estimated low theoretical affinity of peptides from both proteins with iron. However, five peptides (EEEEEEPR, EEEEEDEPR, NQLDPSPR and LDPNPR from L. mutabilis protein hydrolysates, and YQQKPV from casein hydrolysates) showed some molecular potential for iron binding and were further synthesized. L. mutabilis peptides EEEEEDEPR and EEEEEEPR exhibited higher iron-chelating activities (0.393–0.417 μg Fe 2+ /mg peptide) than the casein peptide YQQKPV (0.248 μg Fe 2+ /mg peptide), indicating that L . mutabilis protein has potential for generating peptides with iron-chelating activity after the gastrointestinal digestion. This study gives the molecular and biochemical base for future in vivo studies targeted to validate current results and to evaluate the iron availability.