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.