Identification of native angiotensin-I converting enzyme inhibitory peptides in commercial soybean based infant formulas using HPLC-Q-ToF-MS.

This work evaluates, the presence of native antihypertensive peptides in five soybean-based infant formulas (SBIFs). SBIFs peptide extracts (<10 kDa) and their sub-fractions (5-10 kDa, 3-5 kDa, and <3 kDa) from a variety of samples were obtained by ultrafiltration and ACE inhibitory activity was determined. The highest activities were observed in the smaller (<5 kDa) peptide fractions. A set of peptides present in various SBIFs were studied, and identified using HPLC-Q-ToF-MS. Despite ACE inhibitory activity decreasing after in vitro gastrointestinal digestion, it still remained at a high value (IC50 values of 18.2±0.1 and 4.9±0.1 µg/mL). Peptides resisting the action of gastrointestinal enzymes were identified and compared to previously identified peptides, highlighting the presence of peptide RPSYT. This peptide was synthesised, its antihypertensive and antioxidant activity were evaluated, and its resistance to in vitro gastrointestinal digestion and to high processing temperatures were studied.

Development of a high-performance liquid chromatography-electrospray ionization-quadrupole-time-of-flight-mass spectrometry methodology for the determination of three highly antihypertensive peptides in maize crops.

The simultaneous quantification of three highly antihypertensive peptides (LRP, LSP, and LQP) in six maize crops using novel HPLC-ESI-Q-ToF methodology is presented. The method included the extraction of α-zein proteins from maize, their purification by acetone precipitation, digestion with thermolysin and HPLC separation in a fused-core column. Several MS parameters were optimized to increase sensitivity and reduce spontaneous fragmentation of peptide ions into the ESI source. The ions with m/z 193.1315, 385.2558 (for LRP), 316.1867 (for LSP), and 357.2132 (for LQP) were monitored in the optimization and characterization of the method. In order to improve the repeatability, sensitivity, and the stability of peptides in the sample, the removal of urea was required. The use of two solid-phase extraction methods to remove urea from digested extract was evaluated. For the first time filter-aided sample preparation approach for the study of bioactive peptides in foodstuffs has been proposed. The optimized HPLC-ESI-Q-ToF method was characterized by the evaluation of linearity, LOD, LOQ, precision, and recovery. A study on the existence of matrix interferences was also performed. The developed method was applied to the quantification of LRP, LQP, and LSP peptides in maize lines using the standard addition method. The results showed the highest yield of LSP peptide in EZ11A line and LRP and LQP peptides in A632 line.