Impact of Gastrointestinal Digestion Simulation on the Formation of Angiotensin-I-Converting Enzyme Inhibitory (ACE-I) Peptides from Germinated Lamtoro Gung Flour

Characterization of yellowfin tuna (Thunnus albacares) skin gelatin extracted by bromelain hydrolysis and ultrasound pre-treatment

Yellowfin tuna skin waste is a potential collagen source for gelatin through hydrolysis. Enzymatic hydrolysis is eco-friendly but expensive, necessitating efficiency improvements. Ultrasound pre-treatment enhances efficiency via cavitation effects. This study evaluated the effects of ultrasound amplitude, pre-treatment duration, enzyme concentration, and hydrolysis duration on yield; determined optimal conditions for ultrasound-assisted enzymatic extraction on yield, viscosity, and gel strength; and assessed the gelatin's physicochemical and functional properties. This research consists of three stages, factor screening using one variable at a time, optimization using response surface methodology with Box-Behnken design, and gelatin characterization. The study included three replicates. Screening identified factor ranges for optimization: 5-25 min pre-treatment, 1%-3% enzyme concentration, and 1-5 h hydrolysis. Optimization involved 15 experimental runs, focusing on yield, viscosity, and gel strength. Optimal conditions were 25 min pre-treatment, 1% enzyme concentration, and 2.17 h hydrolysis, yielding 64.08%, 9.29 mPa·s viscosity, and 166.28 bloom gel strength. The optimized gelatin showed emulsifying properties with EAI 50.5 m2/g and ESI 23.80 min, water-oil holding capacities of 192% and 406%, respectively, antioxidant activity of 60.16%, and molecular weight range of 17-160 kDa. The amino acid composition was mainly glycine (29.26%) and proline (18.26%), with 76.95% digestibility. This innovative, environmentally friendly extraction method improved gelatin extraction efficiency from yellowfin tuna skin, supporting a sustainable industry.

Discovery of a novel nanomolar angiotensin-I converting enzyme inhibitory peptide with unusual binding mechanisms derived from Chlorella pyrenoidosa

Chlorella pyrenoidosa (C. pyrenoidosa) has been cultivated in large quantities and proven to be antihypertensive when consumed orally. However, the antihypertensive peptides derived from C. pyrenoidosa remains scarce. In this study, trypsin was chosen to prepare the hydrolysate of C. pyrenoidosa, which was then fractionated by column chromatography. And ninety-nine peptides were identified by LC-MS/MS, after which 10 peptides were chosen by docking-based virtual screening and demonstrated their ability to inhibit ACE. Among them, LVAKA (LV-5) had the lowest IC50 (26.66 μM). LV-5, LKKAP, and PGLRP were identified as non-competitive ACE inhibitory peptides with significant stability under extreme pH and high temperatures conditions. Both in silico and in-vitro simulated gastrointestinal digestion revealed that these three peptides could release ACE inhibitory peptide fragments upon digestion. Sequence optimization of LV-5 led to the discovery of LRAKA (LR-5), which was identified as a novel nanomolar ACE peptide with an IC50 of 350 nM in-vitro and a potent antihypertensive peptide in-vivo. Moreover, molecular dynamic simulation indicated that LR-5 interacted with an unconventional binding site on ACE. These findings underscore the potential of Chlorella as a source of antihypertensive peptides and suggest a promising future for the use of Chlorella-derived peptides in hypertension management.

Precooked Jack Bean [Canavalia ensiformis (L.) DC] Sprout: Generation of Dipeptidyl Peptidase-IV Inhibitory Peptides during Simulated Digestion

Bioactive peptides generated from jack bean sprouts are reported to function as dipeptidyl peptidase IV (DPP-IV) inhibitors. However, no studies have investigated the effect of precooking followed by simulated digestion using pepsin-pancreatin to increase DPP-IV inhibitory peptide generation in jack bean sprouts. Therefore, the present study aimed to explore the generation of DPP-IV inhibitory peptides from precooked jack bean [Canavalia ensiformis (L.) DC] sprouts during simulated digestion with pepsin-pancreatin. The results showed that peptide fractions of the sample hydrolysate with molecular weight <1 kDa exhibited the strongest DPP-IV inhibitory activity (84.77%±0.49%) after simulated digestion. This activity was slightly greater than that (74.12%±0.85%) observed prior to simulated digestion. These findings demonstrate that the DPP-IV inhibitory activity of precooked jack bean sprouts can be retained following simulated digestion. Moreover, our investigation revealed the sequences of two novel peptides following simulated digestion with critical amino acids. The presence of alanine and glycine at the penultimate N-terminus of AAGPKP and LGDLLK confirmed the presence of DPP-IV inhibitors. Both peptide sequences are nontoxic and interact with the catalytic sites of enzymes through hydrogen bonds.

Formation of dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides from Jack Bean (Canavalia ensiformis (L.) DC.) sprout in simulated digestion

Bean sprouts are potential plant proteins that produce DPP-IV inhibitory peptides. These peptides must be stable and active in the brush border membrane of the small intestine to inhibit DPP-IV. The purpose of this research is to evaluate the DPP-IV inhibitory activity of jack bean sprouts using pepsin-pancreatin during simulated digestion, as well as the absorption of these peptides through the everted gut sac method. The results showed that after 180 min of digestion simulation, the Mw < 1 kDa peptide fraction of jack bean hydrolysate, which germinated for 60 h (HG60), had the highest inhibitory activity. The duodenum absorbs most of the peptides with inhibitory activity of 61.77%, which is slightly lower than activity after digestion (62.19%). These outcomes suggest that the DPP-IV inhibitory activity of HG60 can be maintained after digestion and absorption. Two novel peptides KAVGDPI and QGVVLRP identified after absorption contain crucial amino acids confirming as DPP-IV inhibitor.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01343-9.

Impact of Gastrointestinal Digestion Simulation on the Formation of Angiotensin-I-Converting Enzyme Inhibitory (ACE-I) Peptides from Germinated Lamtoro Gung Flour

The germination of lamtoro gung has been shown to increase the angiotensin-I-converting enzyme inhibitory (ACE-I) activity in previous studies. The 48 h germinated flour had the highest ACE-I activity. Administration of the gastrointestinal digestion (GID) simulation with commercial enzymes was expected to increase the ACE-I activity. However, the GID simulation to increase ACE-I in the germinated lamtoro gung flour has not been found. Therefore, this study aimed to evaluate the GID simulation of ACE-I peptides in sprouted lamtoro gung flour. This study also identified and characterised the peptide with the ACE-I activity. The GID simulation was performed using commercial pepsin (pH 2) and pancreatin (pH 7.5). Both simulations occurred at 37 °C for 240 min. The degree of hydrolysis, peptide concentration, and ACE-I activity was analysed. Samples with the highest ACE-I activity were then fractionated and identified, to determine the peptide responsible for the ACE-I activity. The 180 min GID simulation in the test sample showed the highest ACE-I activity (89.70%). This result was supported by an increased degree of hydrolysis (DH) and peptide concentrations throughout the GID simulation. The <1 kDa peptide fraction had the highest inhibitory activity and had the most elevated peptide portion (54.69%). Peptide sequences containing crucial amino acids were found in the <1 kDa peptide fraction. PRPPKPP, PPPPPGARAP, and PFPPSNPPP had proline in the C and N terminal residues. The peptides obtained also had other biological activities, such as a DPP IV inhibitor, an alpha-glucosidase inhibitor, and antioxidative activity. Based on the toxicity prediction, those peptides are non-toxic and safe to consume.