Whey peptide-iron complexes: obtaining, characterization and evaluation of iron pro-oxidant effect and iron bioavailability using Caco-2 cell culture model

Author(s)

Maria Elisa Caetano Silva Abreu

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos
• Defense date: 2017-06-20

Examining board members

Flavia Maria Netto; Amparo de la Asunción Alegría Tóran; Ana Paula Badan Ribeiro; Marco Vinícius Chaud; Solange Guidolin Canniatti Brazaca

• Advisor: Flavia Maria Netto; Maria Teresa Bertoldo Pacheco

Abstract

Food fortification with iron has been challenging, since in salt form, as commonly applied, iron shows low bioavailability and promotes undesirable sensory changes and lipid oxidation. The present work aimed to synthesize and characterize peptide-iron complexes using FeCl2 or FeSO4 as iron precursor compounds, and to study possible effects of complexation, concerning in vitro iron bioavailability and its pro-oxidant effect. To synthesize the complexes, whey protein isolate (WPI), WPI hydrolyzed with pancreatin and its fractions obtained by ultrafiltration using a 5 kDa cut off membrane, were used as ligands. The fluorescence spectra of ligands showed dramatic decrease in fluorescence intensity as iron concentration increased. Possibly, ligand conformation changes during the process of iron coordination led to changes in tryptophan (Trp) microenvironment. Iron coordination by the ligands, for both iron sources, occurred mainly through bidentate coordination mode with carboxyl groups, evidenced by IR bands assigned to the vibrational modes asymmetric and symmetric stretching of COO-Fe bond. The iron source influenced the complex structure, possibly due to the counterions chloride and sulfate, which exert a crucial role in the conformation of the ligand and, consequently, the formed complex. Iron coordination by all the ligands favored the formation of complexes stable under gastrointestinal in vitro digestion, leading to bioaccessibility > 85% in all cases. Nevertheless, the complexes synthesized with low-molecular-mass peptides (MM<5 kDa) and FeCl2 led to higher ferritin synthesis in Caco-2 cells than ferrous sulfate. This fact suggests that the pathway of iron uptake in its complexed form is related not only to the capacity to protect iron during gastrointestinal tract and to take it near to the enterocyte, but also to the normal ligand pathway. The iron source influenced the in vitro bioavailability, possibly due to the differences in complexes structures, evidencing the great importance of the iron source choice. Besides the in vitro bioavailability aspect, iron complexation led to decrease in its pro-oxidant effect, evidenced by the reduction of primary and secondary lipid oxidation products in oil-in-water emulsions, in relation to the mineral free form. Emulsions containing peptide-iron complexes showed peroxide and hexanal formation around 60-80% and 85-100% lower than the emulsions containing iron in salt form, respectively. The addition of peptide-iron complexes into the emulsions resulted in much lower lipid oxidation possibly due to the antioxidant activity of the peptides and their capacity to keep iron coordinated and therefore less reactive. The peptide-iron complex is therefore a promising alternative for food fortification instead of ferrous sulfate, one of the most widely used salts for this practice. The use of this complex shows potential to increase iron absorption and to decrease its pro-oxidant effect. Thus, it can favor the reduction of undesirable sensory changes in food products, diminish the side effects related to free iron, as well as the oxidative damages in the cell membranes in the organism (AU)

• FAPESP's process: 13/10356-7 - Iron-whey peptide chelate: preparation, characterization and evaluation of pro-oxidant effect of iron and its bioavailability in a Caco-2 cell culture model
• Grantee: Maria Elisa Caetano Silva Abreu
• Support Opportunities: Scholarships in Brazil - Doctorate