The Stability of Food Bioactive Peptides in Blood: An Overview

Production, characterisation, and biological properties of Tenebrio molitor-derived oligopeptides

Three protein hydrolysates from Tenebrio molitor were obtained by enzymatic hydrolysis employing two food-grade proteases (i.e. Alcalase and Flavourzyme), and a complete characterisation of their composition was done. The digestion-derived products were obtained using the INFOGEST protocol. In vitro antioxidant activity and anti-inflammatory activities were evaluated. Tenebrio molitor flour and the protein hydrolysates showed a high ability to scavenge the DPPH radical (EC50 values from 0.30 to 0.87 mg/mL). The hydrolysate obtained with a combination of the two food-grade proteases could decrease the gene expression of pro-inflammatory genes after being digested. Furthermore, the peptidome was fully determined for the first time for T. molitor hydrolysates and digests, and 40 peptides were selected based on their bioactivity to be evaluated by in silico tools, including prediction tools and molecular docking. These results provide new perspectives on the use of edible insects as sustainable and not nutritionally disadvantageous food for human consumption.

Identification, characterization, and molecular docking of immunomodulatory oligopeptides from bioavailable hempseed protein hydrolysates

Promoting dietary patterns in which the content of vegetables is higher than the current consumption of them is one of the strategies to achieve a sustainable food system while promoting health in humans. Hemp (Cannabis sativa L.) protein contains bioactive peptides that can be released via enzymatic hydrolysis. These peptides must reach the target organ in order to potentially exert bioactivity and regulate specific metabolic pathways. The peptides contained in two bioavailable hempseed protein hydrolysates (bioHPHs) showing anti-inflammatory activity were identified using a transwell system employing CACO-2 cell culture as absorption model and subjected to in silico analysis to select 10 unique peptides. These sequences were chemically synthetized to verify their activity in primary human monocytes (assessing gene expression of IL-1β, IL-6, TNF-α, IL-4, IL-10, and TLR4), in addition to evaluate the interaction with TRL4/MD2 by molecular docking. Six peptides (DDNPRRF, SRRFHLA, RNIFKGF, VREPVFSF, QADIFNPR and SAERGFLY) showed high immunomodulatory activity in in vitro and the mechanisms of interaction with TLR4/MD2 were described. Bioavailable anti-inflammatory hempseed-derived peptides were identified, and their activity verified, suggesting the health benefits that the ingestion of HPHs could exert in humans. These findings open new opportunities for developing nutritional strategies with hemp as a dietary source of biopeptides to prevent the development and progression of inflammatory-related diseases.

Impact of C- and N-terminal protection on the stability, metal chelation and antimicrobial properties of calcitermin

The main limitation to the use of antimicrobial peptides (AMPs) as regular drugs, against antibiotic and antifungal resistance, mainly relates to their rapid degradation by proteolytic enzymes. The introduction of suitable structural changes in the peptide chain can make the peptide less susceptible to the action of proteases, thus overcoming this problem. To improve the plasma stability of calcitermin, a metal-chelating AMP present in the human respiratory tract and investigated in the present study, C- and/or N- terminal modifications have been introduced in the native sequence. Evaluation of peptide stability has been performed to determine the half-life times in human plasma of both native calcitermin and its derivatives. However, the protection of the peptide termini can also affect its metal coordination behaviour. Thus, the characterization of Zn2+ and Cu2+ complexes has been performed by means of several techniques, including potentiometry, high-resolution mass spectrometry, UV-Vis, circular dichroism and EPR. On the basis of the obtained results, it was possible to compare the biological activity of the studied systems, taking into account both the metal-binding ability and the peptide stability to search for a link among them. A significant result of this study is that the N-terminal protection increases the calcitermin half-life over seven times and the formation of metal complexes confers resistance towards degradation almost doubling its half-life.

Oxidative Stress Protection by Canary Seed (Phalaris canariensis L.) Peptides in Caco-2 Cells and Caenorhabditis elegans

During oxidative stress, degenerative diseases such as atherosclerosis, Alzheimer’s, and certain cancers are likely to develop. Recent research on canary seed (Phalaris canariensis) peptides has demonstrated the high in vitro antioxidant potential. Thus, this study aimed to assess the cellular and in vivo antioxidant capacity of a low-molecular-weight (<3 kDa) canary seed peptide fraction (CSPF) using Caco-2 cells and the Caenorhabditis elegans model. The results show that the CSPF had no cytotoxicity effect on Caco-2 cells at any tested concentration (0.3−2.5 mg/mL). Additionally, the cellular antioxidant activity (CAA) of the CSPF was concentration-dependent, and the highest activity achieved was 80% by the CSPF at 2.5 mg/mL. Similarly, incubation with the CSPF significantly mitigated the acute and chronic oxidative damage, extending the lifespan of the nematodes by 88 and 61%, respectively. Furthermore, it was demonstrated that the CSPF reduced the accumulation of reactive oxygen species (ROS) to safe levels after sub-lethal doses of pro-oxidant paraquat. Quantitative real-time PCR revealed that the CSPF increased the expression of oxidative-stress-response-related gene GST-4. Overall, these results show that the CSPFs relied on GST-4 upregulation and scavenging of free radicals to confer oxidative stress protection and suggest that a CSPF can be used as a natural antioxidant in foods for health applications.