Ultrasonication coupled to enzymatic hydrolysis of soybean okara proteins for producing bioactive and bioavailable peptides

This work was aimed to explore the antioxidative properties, bioavailability and the safety of bioactive peptides obtained by the enzymatic hydrolysis of ultrasound-treated (UO) and untreated (nUO) soybean okara proteins. Particularly, the peptidomic profiles of both hydrolysates were examined using an untargeted metabolomics technique for suspect screening that was specifically designed for the profiling of short-chain peptides and relied on ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) and bioinformatics.
Next, both UO and nUO hydrolysates reduce Dipeptidyl peptidase-IV (DPP-IV) enzyme activity until 39.54 ± 0.26 % and 43.29 ± 0.36 % respectively and inhibit angiotensin converting enzyme (ACE) activities by 30.54 ± 0.42 % and 30.76 ± 0.02 %, respectively. Moreover, they demonstrate to exerted antioxidant properties. Particularly, they show a comparable in vitro antioxidant activity but when the oxidative stress is induced by H2O2 in Caco-2 cells, UO hydrolysate is more active in lowering the levels of reactive oxygen species (ROS) and of lipid peroxidation induced of 48% and 20% respectively.
In addition, UO- and nUO-derived peptides trans-epithelial transported by human differentiated intestinal cell monolayer, were identified. Lastly, the possible hepatotoxicity of UO and nUO hydrolysates in HepG2 cells has not been observed by measuring alanine transferase (ALT) and aspartate transferase (AST) levels and cytotoxic effects.