Abstract
Albumin is the major fraction of quinoa protein that is characterized as having high nutritional value. However, until now, scant information is available on the bioactivity of quinoa albumin or its hydrolysates. To promote its usage, we extracted albumin in this study from quinoa bran assisted with cellulase and hemicellulose, and hydrolyzed it by alcalase and trypsin to produce bioactive peptides. The hydrolysates (QBAH) were purified by gel filtration and reversed-phase high-performance liquid chromatography (RP-HPLC), followed by identification using liquid chromatography–mass spectrometry (LC-MS/MS). Furthermore, based on in silico analysis, one angiotensin-I converting enzyme (ACE)-inhibitory and antioxidant peptide, RGQVIYVL (946.6 Da), and two antioxidant peptides, ASPKPSSA (743.8 Da), and QFLLAGR (803.5 Da), from QBAH were synthesized. RGQVIYVL showed a high ACE-inhibitory activity (IC50 = 38.16 μM) with competitive mode of inhibition, and showed significant antihypertensive effect in spontaneously hypertensive rats at a concentration of 100–150 mg/kg body weight (bw). Molecular docking simulation showed that it could interact with the active ACE site via hydrogen bonds with high binding power. Moreover, RGQVIYVL, ASPKPSSA, and QFLLAGR all demonstrated high ·OH scavenging activity (IC50 = 61.69–117.46 μM), ABTS+ scavenging activity (58.29–74.28%) and Fe2+ chelating ability (32.54–82.48% at 0.5 mg/mL). They could also retain activity after gastrointestinal enzyme digestion. These results indicate that quinoa albumin is a potential source of bioactive peptides possessing antioxidant and ACE-inhibitory activities.
Highlights
In the recent past, food-derived bioactive peptides have attracted much attention for their potential to serve as natural alternatives or complements to synthetic drugs
Chelating ability (32.54–82.48% at 0.5 mg/mL). They could retain activity after gastrointestinal enzyme digestion. These results indicate that quinoa albumin is a potential source of bioactive peptides possessing antioxidant and angiotensin-I converting enzyme (ACE)-inhibitory activities
The subjection to hydrolysis by alcalase was followed by trypsin, and the hydrolysis degree of Quinoa Bran Albumin Hydrolysates (QBAH) was 24.26% ± 3.61%, while the ACE inhibition activity and ·OH scavenging ability were 62.38% ± 5.64% and 51.77% ± 5.15%, respectively
Summary
Food-derived bioactive peptides have attracted much attention for their potential to serve as natural alternatives or complements to synthetic drugs. These bioactive peptides are usually specific and small protein fragments (2–20 amino acids long) which are inactive within the parent protein but may reveal some functions such as antioxidant, antihypertension, anticancer, and antimicrobial activity after releasing from their protein sources [1]. It is important to inhibit oxidation reaction and the formation of excessive free radicals occurring in the body Both hypertension and oxidative stress have a critical link with diet; control and improvement of diet would be the easiest option to handle both risk factors [6]. The number of studies focused on their in vivo antihypertension, structural bioinformatics, bioavailability, and action mechanism is limited [3,7,8,9,10,11]
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