Bovine milk antioxidant properties: effect of in vitro digestion and identification of antioxidant compounds

Abstract

Milk proteins contained encrypted in their sequence biologically active components that can be released by enzymatic hydrolysis. Among the biological activities recognized in milk components, the antioxidant activity is of great interest.\ud The objective of the present study was to analyse the antioxidant properties of whole, semi-skimmed and skimmed milk during simulated gastrointestinal digestion and to identify the compounds responsible for the antioxidant activity. Simulated digestion\ud increased the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS)+ radical scavenging activity of milk. In digested whole milk, the main contribution to ABTS+ radical scavenging activity was due to high molecular weight fraction (>3 kg.mol−1).\ud For semi-skimmed and skimmed milk, the main contribution was due to low molecular weight fraction (<3 kg.mol−1). Twelve major peaks were collected from low molecular weight fraction of digested skimmed milk by reversed-phase high-performance liquid chromatography and evaluated for their ABTS+ radical scavenging activity. Among the different fractions, three (F2, F3 and F5) showed high ABTS+ and hydroxyl radical scavenging activity and lipid peroxidation inhibitory capacity. The compounds (free\ud amino acids and peptides) present in these fractions were identified with nano-LCQTOF MS/MS analysis. The amino acids tryptophan and tyrosine seemed fundamental in the ABTS+ and hydroxyl radical scavenging capacities whereas the amino acids\ud phenylalanine and histidine played an important role in the lipid peroxidation inhibitory activity of the peptides. The results reported in this study suggested that milk proteins could act as a carrier for the delivery of antioxidant compounds in the gastrointestinal tract possibly protecting the gastrointestinal tract itself from the oxidative damage

Bioprospecting for Bioactive Peptide Production by Lactic Acid Bacteria Isolated from Fermented Dairy Food

“…In fact, free radicals are deactivated by peptides containing hydrophobic and aromatic amino acids (such as Y, H, P, W) and selected free amino acids (Y and C) [101,117]. In particular, the presence of Y and W residues in the peptides sequences is considered essential for a significant increase of the antioxidant effect, because of its strong ability to donate a proton [65,118,119]. Actually, their occurrence into the sequences of dipeptides is usually recognized as responsible for antioxidant activities [120].…”

Biological activities and peptidomic profile of in vitro-digested cow, camel, goat and sheep milk

“…The ABTS assay was carried out as described above. The capacity to scavenge hydroxyl radicals was evaluated according to Tagliazucchi, Helal, Verzelloni, & Conte (2016c). In the assay, 50 μL of appropriately diluted samples or standard (vitamin C) were mixed with 50 μL of TPTZ (2,4,6-tri(2pyridyl)-S-triazine) at a concentration of 3 mmol L −1 , 50 μL of 3 mmol L −1 FeSO4, and 50 μL of 0.01% (v/v) hydrogen peroxide, in a clear bottom 96-well plate.…”

Microbial transglutaminase enhances antioxidant activity of yogurt through altering pattern of water‐soluble peptides and increasing release of amino acids

“…It should be noted that many peptides in the treated yogurt contained hydrophobic amino acid residues, such as valine, leucine, proline, cysteine, histidine and methionine (Table ). It has been confirmed that tyrosine and cysteine residues can contribute the radical scavenging property to peptides, whereas proline, valine, leucine, phenylalanine and histidine in peptides play roles in inhibiting lipid peroxidation (Tagliazucchi et al ., ). Different from the microbial transglutaminase‐treated yogurt, the β‐casein‐derived peptides, including PYPQ, VLPVPQKAVPYPQ and PVPQKAVPYPQ, were considered the antioxidative peptides in the control yogurt (Table ), as their domain PYPQ has been confirmed to participate in antioxidant activity (Rival et al .,).…”

“…Different from the microbial transglutaminase‐treated yogurt, the β‐casein‐derived peptides, including PYPQ, VLPVPQKAVPYPQ and PVPQKAVPYPQ, were considered the antioxidative peptides in the control yogurt (Table ), as their domain PYPQ has been confirmed to participate in antioxidant activity (Rival et al .,). Additionally, the κ‐casein‐derived peptide VLSRYPSYGLN and PIQYVLSRYPSY were also considered to have antioxidant properties as the sequence YPS was reported to provide antioxidative feature to the peptide AYPS, SRYPS, and RYPS (De Gobba et al ., ; Tagliazucchi et al ., ). Moreover, a long peptide QPTTMARHPHPHLSFMAI (κ‐casein 82‐99) found in the control yogurt might be the precursor of an antioxidant peptide HPHPHLSF (Gómez‐Ruiz et al ., ).…”