Purification and characterization of antioxidant peptide from hoki (Johnius belengerii) frame protein by gastrointestinal digestion

Assessment of antioxidant properties of membrane ultrafiltration peptides from mungbean meal protein hydrolysates

BACKGROUND

Bioactive peptides can prevent damage associated with oxidative stress in humans when consumed regularly. Recently, peptides have attracted immense interest because of their beneficial functional properties, safety and little or no side effects when used at high concentration. Most antioxidant peptides are small in size, less than 1 kDa, and contains a high proportion of hydrophobic amino acid. Particularly, tyrosine, leucine, alanine, isoleucine, valine, lysine, phenyalanine, cysteine, methionine and histidine in peptide chain exhibited high antioxidant activity. Mungbean meal protein (MMP) is highly abundant in hydrophobic amino acids. It indicated that MMP might be a good source of antioxidants. Therefore, the objectives were to optimize the conditions used to generate mungbean meal protein hydrolysate (MMPH) with antioxidant activity from bromelain and to investigate the antioxidant activities of different molecular weight (MW) peptide fraction.

METHODS

Response Surface Methodology (RSM) was used for screening of the optimal conditions to produce MMPH. After that MMPH was fractionated using ultrafiltration membranes with different MW distributions. Crude-MMPH and four fractions were investigated for five antioxidant activities: 2,2,1-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, superoxide, ferric reducing antioxidant power (FRAP) and metal ion chelation activity.

RESULTS

The optimal condition to produce the MMPH was 15% (w/w) of bromelain and hydrolysis time for 12 h which showed the greatest DPPH and ABTS radical scavenging activity. After mungbean protein from optimal condition was separated based on different molecular weight, the DPPH radical scavenging activity was the highest for the F4 (less than 1 kDa) peptide fraction. Metal ion chelating activity was generally weak, except for the F4 that had a value of 43.94% at a protein concentration of 5 mg/mL. The F4 also exhibited high hydroxyl and superoxide activities (54 and 65.1%), but moderate activity for ferric reducing antioxidant power (0.102 mmole Fe2+/g protein) compared to other peptide fractions and crude-MMPH. Molecular weight and amino acid were the main factors that determined the antioxidant activities of these peptide fractions. Results indicated that F4 had strong antioxidant potentials.

DISCUSSION

The lowest MW fraction (less than 1 kDa) contributed to the highest DPPH, superoxide, hydroxyl and metal chelation activity because influence of low MW and high content of hydrophobic amino acid in peptide chain. Results from this study indicated that MMPH peptides donate protons to free radicals because they had significantly high DPPH value compared to superoxide, hydroxyl and FRAP, which reactions were electron donation. Moreover, MMPH peptides had the ability to inhibit transition metal ions because of highly abundant glutamic acid and aspartic acid in peptide chain.

Production of antioxidant peptide fractions from a by-product of tomato processing: mass spectrometry identification of peptides and stability to gastrointestinal digestion

In this study, proteins were extracted from tomato seeds, the main by-product of tomato processing. The incubation for 138.62 min coupled with 3% alcalase was observed to be optimum to produce a tomato seed protein hydrolysate (TSPH) with the highest antioxidant properties. Under these conditions, predicted TSPH activities were 62.99% scavenging of DPPH radicals and 54.81% reduction of phosphomolybdate. Separation of TSPH by ultrafiltration provided three fractions (UF1-UF3) of which, UF3 (< 3 kDa) showed the strongest activity (73.15% DPPH scavenging and 60.1% phosphomolybdate reduction). UF3 was further separated by RP-HPLC into sub-fractions F1-F6. Biological testing found that F2 and F4 were the most active in scavenging DPPH radicals (60.36 and 21.23%) and reducing phosphomolybdate (57.3 and 48.0%). LC-ESI-MS/MS analysis showed that the higher activity of F2 might be explained by the presence of more peptides that contained tyrosine and histidine, known to enhance antioxidant activity through hydrogen or electron transfer. In the simulated gastrointestinal digestion test, peptides in F2 were more resistant compared to those in F4. These findings indicate that peptide fraction F2 might be more useful in the formulation of functional foods because of its greater antioxidant activity and resistance to digestion.

Changes in the amino acid profiles and free radical scavenging activities of Tenebrio molitor larvae following enzymatic hydrolysis

Tenebrio molitor (T. molitor) larvae provide food at low environmental cost and contribute positively to livelihoods. In this research, we compared the amino acids compositions and antioxidant activities of various extracts of T. molitor to enhance their quality as food. For the comparison, distilled water extracts, enzymatic hydrolysates, and condensed enzymatic hydrolysates of T. molitor larvae were prepared. Their amino acids (AAs) profiles and antioxidant activities, including ferric-reducing antioxidant power, oxygen radical absorption capacity, and DPPH, hydroxyl radical, and hydrogen peroxide radical scavenging properties assay were analyzed. DW extracts had the lowest AAs contents and antioxidant activity compared with enzymatic extracts. Condensed hydrolysates with a combination of alcalase and flavourzyme (C-A+F) exhibited the highest levels of total free AAs (11.1759 g/100 g). C-A+F produced higher total hydrolyzed AAs (32.5292 g/100 g) compared with the other groups. The C-A+F possessed the strongest antioxidant activity. Notably, the antioxidant activities of the hydrolysates and the total hydrolyzed AAs amount were correlated. Taken together, our findings showed that C-A+F was a promising technique for obtaining extracts of T. molitor larvae with antioxidant activity as potential nutritious functional food.

Vicilin-A major storage protein of mungbean exhibits antioxidative potential, antiproliferative effects and ACE inhibitory activity

Enzymatic hydrolysates of different food proteins demonstrate health benefits. Search for diet related food protein hydrolysates is therefore of interest within the scope of functional foods. Mungbean is one of the popular foods in India because of rich protein source. In this study, mungbean vicilin protein (MBVP) was enzymatically hydrolysed by alcalase and trypsin under optimal conditions. We have studied the antioxidant, antiproliferative and angiotensin-converting enzyme (ACE) inhibitory activities of mungbean vicilin protein hydrolysate (MBVPH) vis-a-vis alcalase-generated mungbean vicilin protein hydrolysate (AMBVPH) and trypsin-generated mungbean vicilin protein hydrolysate (TMBVPH). The results showed that MBVPH exhibited higher antioxidant potential, ACE inhibitory and antiproliferative activities than MBVP. The alcalase treated hydrolysate displayed highest ACE inhibitory activity with IC50 value of 0.32 mg protein/ml. The MBVP showed significant antiproliferative activity against both MCF-7 and MDA-MB-231 breast cancer cells at the doses between 0.2-1.0 mg/ml. The data suggested that MBVPH can be utilized as physiologically active functional foods with sufficient antihypertensive activity. The results indicate that mungbean can be utilized as a rich resource of functional foods.

Separation and Characterization of Antioxidative and Angiotensin Converting Enzyme Inhibitory Peptide from Jellyfish Gonad Hydrolysate

The gonad of jellyfish (RhopilemaesculentumKishinouye), containing high protein content with a rich amino acid composition, is suitable for the preparation of bioactive peptides. Jellyfish gonad was hydrolysed with neutral protease to obtain jellyfish gonad protein hydrolysate (JGPH), which was then purified sequentially by ultrafiltration, gel filtration chromatography, and RP-HPLC. The peptides were characterized with HPLC-MS/MS. One peptide with amino acid sequence Ser-Tyr (SY) was identified and synthesized, which showed good ACE inhibitory and antioxidant activity. The IC50 of this peptide on DPPH, ·OH, super oxygen anion scavenging activities, and ACE inhibitory activity are 84.623 μM, 1177.632 μM, 456.663 μM, and 1164.179 μM, respectively. The anchor in the binding site of SY and ACE C-domain (ACE-C) was obtained by molecular simulations. The results showed that the dipeptide purified from jellyfish gonad protein hydrolysates can be used as functional food material and is helpful in the study of antioxidant and inhibition of ACE.

Effects of Maillard-type caseinate glycation on the preventive action of caseinate digests in acrylamide-induced intestinal barrier dysfunction in IEC-6 cells

Dietary acrylamide has attracted widespread concern due to its toxic effects; however, its adverse impact on the intestines is less assessed. Protein glycation of the Maillard-type is widely used for property modification, but its potential effect on preventive efficacy of protein digest against the acrylamide-induced intestinal barrier dysfunction is quite unknown. Caseinate was thus glycated with lactose. Two tryptic digests from the glycated caseinate and untreated caseinate (namely GCN digest and CN digest) were then assessed for their protective effects against acrylamide-induced intestinal barrier dysfunction in the IEC-6 cell model. The results showed that acrylamide at 1.25–10 mmol L⁻¹ dose-dependently had cytotoxic effects on IEC-6 cells, leading to decreased cell viability and increased lactate dehydrogenase release. Acrylamide also brought about barrier dysfunction, including decreased trans-epithelial electrical resistance (TEER) value and increased epithelial permeability. However, the two digests at 12.5–100 μg mL⁻¹ could alleviate this dysfunction via enhancing cell viability by 70.2–83.9%, partly restoring TEER values, and decreasing epithelial permeability from 100% to 76.6–94.1%. The two digests at 25 μg mL⁻¹ strengthened the tight junctions via increasing tight junction proteins ZO-1, occludin, and claudin-1 expression by 11.5–68.6%. However, the results also suggested that the GCN digest always showed lower protective efficacy than the CN digest in the cells. It is concluded that Maillard-type caseinate glycation with lactose endows the resultant tryptic digest with impaired preventive effect against acrylamide-induced intestinal barrier dysfunction, highlighting another adverse effect of the Maillard reaction on food proteins.

Glycated caseinate digest of the Maillard-type has lower protective action than caseinate digest against acrylamide-induced barrier dysfunction in IEC-6 cells.

Structural Characterization of a Tetrapeptide from Sesame Flavor-Type Baijiu and Its Preventive Effects against AAPH-Induced Oxidative Stress in HepG2 Cells

Peptides are rarely reported from Chinese Baijiu (Chinese liquor) because they are often present in very low concentrations in the complex matrix. A tetrapeptide, Ala-Lys-Arg-Ala (AKRA), was recently identified by high-performance liquid chromatography and quadrupole-time-of-flight-mass spectrometry (HPLC-Q-TOF-MS) from sesame flavor-type Baijiu at a concentration of 8.497 ± 0.753 μg/L (P > 0.05), and this tetrapeptide showed preventive effects against 2,2'-azobis(2-methylpropanimidamidine) dihydrochloride (AAPH)-induced oxidative stress in HepG2 cells. The cellular antioxidant activity assay results showed that AKRA protected AAPH-induced oxidative stress in HepG2 cells in a concentration-dependent manner. Pretreatment of the cells for 2 h with AKRA (0.38-1.50 mg/mL) caused strong intracellular reactive oxygen species (ROS) scavenging activities and prevented a decrease in reduced glutathione (GSH) and increases in oxidized glutathione (GSSG) and malondialdehyde (MDA). In addition, AKRA treatment prevented significant decreases in glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) induced by AAPH. Thus, AKRA treatment ameliorated AAPH-induced oxidative stress in HepG2 cells. This study will be important for the design and regulation of functional Baijiu production.

Peptides: Production, bioactivity, functionality, and applications

Production of peptides with various effects from proteins of different sources continues to receive academic attention. Researchers of different disciplines are putting increasing efforts to produce bioactive and functional peptides from different sources such as plants, animals, and food industry by-products. The aim of this review is to introduce production methods of hydrolysates and peptides and provide a comprehensive overview of their bioactivity in terms of their effects on immune, cardiovascular, nervous, and gastrointestinal systems. Moreover, functional and antioxidant properties of hydrolysates and isolated peptides are reviewed. Finally, industrial and commercial applications of bioactive peptides including their use in nutrition and production of pharmaceuticals and nutraceuticals are discussed.

Current trends and perspectives of bioactive peptides

The remarkable growth of therapeutic peptide development in the past decade has led to a large number of market approvals and the market value is expected to hit $25 billion by 2018. This significant market increase is driven by the increasing incidences of metabolic and cardiovascular diseases and technological advancements in peptide synthesis. For this reason, the search for bioactive peptides has also increased exponentially. Many bioactive peptides from food and nonfood sources have shown positive health effects yet, obstacles such as the need to implement efficient and cost-effective strategies for industrial scale production, good manufacturing practices as well as well-designed clinical trials to provide robust evidence for supporting health claims continue to exist. Several other factors such as the possibility of allergenicity, toxicity and the stability of biological functions of the peptides during gastrointestinal digestion would need to be addressed.

Antioxidant and emulsion properties of freshwater carps (Catla catla, Labeo rohita, Cirrhinus mrigala) protein hydrolysates prepared using flavorzyme

Fish protein hydrolysates (FPHs) were prepared from freshwater carps (Catla catla, Labeo rohita, and Cirrhinus mrigala) using flavorzyme at different degrees of hydrolysis (DHs) ranging from 5 to 20%. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical-scavenging activity of the FPHs prepared from the three species were in the range of 50-82%; the ferric reducing power of the FPHs prepared from catla was the highest. The linoleic acid peroxidation inhibition activity of the prepared FPHs varied from 71 to 91%. The emulsion activity index of the FPHs prepared from catla and rohu decreased significantly with an increase in the DH (p < 0.05). The emulsion stability index of the FPHs prepared from the three species was the highest at 20% DH. FPHs prepared from freshwater carps possess good antioxidant and surface-active properties and are therefore suitable to be used as natural antioxidants in health-food formulation and as water-soluble antioxidants in the food-processing industry.

Effect of processing conditions on degree of hydrolysis, ACE inhibition, and antioxidant activities of protein hydrolysate from Acetes indicus

Protein hydrolysate was prepared from Acetes indicus which is a major bycatch among non-penaeid prawn landings of India. Hydrolysis conditions (enzyme to substrate ratio and time) for preparing protein hydrolysates using alcalase enzyme were optimized by response surface methodology using central composite design. The optimum conditions for enzyme-substrate ratio (mL/100 g) of 1.57, 1.69, 1.60, 1.56, and 1.50 and for hydrolysis time of 97.18, 96.5, 98.15 min, 102.48, and 88.44 min were established for attaining maximum yield, degree of hydrolysis, 2,2-diphenyl-1-picrylhydrazyl, angiotensin I-converting enzyme-inhibiting activity, and metal-chelating activity, respectively. ABTS radical scavenging activity and reducing power assay of optimized protein hydrolysate were found to be increased with the increase in concentration. The higher value of 7.04 (μM Trolox/g), 87.95, and 77.24%, respectively for DPPH, ACE, and metal-chelating activity indicated that the A. indicus protein hydrolysates have beneficial biological properties that could be well-utilized in the application of functional foods and nutraceuticals. Graphical abstract ᅟ.

Characterization, Preparation, and Purification of Marine Bioactive Peptides

Marine bioactive peptides, as a source of unique bioactive compounds, are the focus of current research. They exert various biological roles, some of the most crucial of which are antioxidant activity, antimicrobial activity, anticancer activity, antihypertensive activity, anti-inflammatory activity, and so forth, and specific characteristics of the bioactivities are described. This review also describes various manufacturing techniques for marine bioactive peptides using organic synthesis, microwave assisted extraction, chemical hydrolysis, and enzymes hydrolysis. Finally, purification of marine bioactive peptides is described, including gel or size exclusion chromatography, ion-exchange column chromatography, and reversed-phase high-performance liquid chromatography, which are aimed at finding a fast, simple, and effective method to obtain the target peptides.

The decreased growth performance and impaired immune function and structural integrity by dietary iron deficiency or excess are associated with TOR, NF-κB, p38MAPK, Nrf2 and MLCK signaling in head kidney, spleen and skin of grass carp (Ctenopharyngodon idella)

This study was conducted to investigate the effects of dietary iron on the growth, and immune function and structural integrity in head kidney, spleen and skin as well as the underlying signaling of young grass carp (Ctenopharyngodon idella). Total 630 grass carp (242.32 ± 0.58 g) were fed diets containing graded levels of iron at 12.15 (basal diet), 35.38, 63.47, 86.43, 111.09, 136.37 mg/kg (diets 2-6 were added with ferrous fumarate) and 73.50 mg/kg (diet 7 was added with ferrous sulfate) diet for 60 days. Then, a challenge test was conducted by infection of Aeromonas hydrophila for 14 days. The results firstly showed that compared with optimal iron level, iron deficiency decreased lysozyme (LZ) and acid phosphatase (ACP) activities, complement 3 (C3), C4 and immunoglobulin M (IgM) contents and down-regulated the mRNA levels of antibacterial peptides, anti-inflammatory cytokines, inhibitor of κBα (IκBα), target of rapamycin (TOR) and ribosomal protein S6 kinase 1 (S6K1), whereas up-regulated the mRNA levels of pro-inflammatory cytokines, nuclear factor kappa B (NF-κB) p65, IκB kinases β (IKKβ) and eIF4E-binding protein (4E-BP) in head kidney and spleen of young grass carp (P < 0.05), indicating that iron deficiency impaired immune function in head kidney and spleen of fish. Secondly, iron deficiency down-regulated the mRNA levels of B-cell lymphoma-2 (Bcl-2), myeloid cell leukemia 1 (Mcl-1), and inhibitor of apoptosis protein (IAP), and decreased activities and mRNA levels of antioxidant enzymes, down-regulated the mRNA levels of NF-E2-related factor 2 (Nrf2) and tight junction complexes, and up-regulated mRNA levels of cysteinyl aspartic acid-protease (caspase) -2, -3, -7, -8, -9, apoptotic protease activating factor-1 (Apaf-1), Bcl-2 associated X protein (Bax), Fas ligand (FasL), p38 mitogen-activated protein kinase (p38MAPK), Kelch-like ECH-associating protein (Keap) 1a, Keap1b, claudin-12 and myosin light chain kinase (MLCK), and increased malondialdehyde (MDA), protein carbonyl (PC) and reactive oxygen species (ROS) contents in head kidney and spleen of young grass carp (P < 0.05), indicating that iron deficiency impaired structural integrity in head kidney and spleen of fish. Thirdly, iron deficiency increased skin hemorrhage and lesion morbidity, and impaired immune function and structural integrity in skin of fish. Fourthly, iron excess decreased growth and impaired the immune function and structural integrity in head kidney, spleen and skin of fish. Besides, in young grass carp, based on PWG and ability against skin hemorrhage and lesion, the efficacy of ferrous fumarate relative to ferrous sulfate was 140.32% and 126.48%, respectively, and the iron requirements based on PWG, ability against skin hemorrhage and lesion, ACP activities and MDA contents in head kidney and spleen were estimated to be 75.65, 87.03, 79.74, 78.93, 83.17 and 82.14 mg/kg diet (based on ferrous fumarate), respectively.

Marine Fish Proteins and Peptides for Cosmeceuticals: A Review

Marine fish provide a rich source of bioactive compounds such as proteins and peptides. The bioactive proteins and peptides derived from marine fish have gained enormous interest in nutraceutical, pharmaceutical, and cosmeceutical industries due to their broad spectrum of bioactivities, including antioxidant, antimicrobial, and anti-aging activities. Recently, the development of cosmeceuticals using marine fish-derived proteins and peptides obtained from chemical or enzymatical hydrolysis of fish processing by-products has increased rapidly owing to their activities in antioxidation and tissue regeneration. Marine fish-derived collagen has been utilized for the development of cosmeceutical products due to its abilities in skin repair and tissue regeneration. Marine fish-derived peptides have also been utilized for various cosmeceutical applications due to their antioxidant, antimicrobial, and matrix metalloproteinase inhibitory activities. In addition, marine fish-derived proteins and hydrolysates demonstrated efficient anti-photoaging activity. The present review highlights and presents an overview of the current status of the isolation and applications of marine fish-derived proteins and peptides. This review also demonstrates that marine fish-derived proteins and peptides have high potential for biocompatible and effective cosmeceuticals.

Preparation of Antioxidant Peptides from Salmon Byproducts with Bacterial Extracellular Proteases

Bacterial extracellular proteases from six strains of marine bacteria and seven strains of terrestrial bacteria were prepared through fermentation. Proteases were analyzed through substrate immersing zymography and used to hydrolyze the collagen and muscle proteins from a salmon skin byproduct, respectively. Collagen could be degraded much more easily than muscle protein, but it commonly showed weaker antioxidant capability. The hydrolysate of muscle proteins was prepared with crude enzymes from Pseudoalteromonas sp. SQN1 displayed the strongest activity of antioxidant in DPPH and hydroxyl radical scavenging assays (74.06% ± 1.14% and 69.71% ± 1.97%), but did not perform well in Fe²⁺ chelating assay. The antioxidant fractions were purified through ultrafiltration, cation exchange chromatography, and size exclusion chromatography gradually, and the final purified fraction U2-S2-I displayed strong activity of antioxidant in DPPH, hydroxyl radical scavenging assays (IC₅₀ = 0.263 ± 0.018 mg/mL and 0.512 ± 0.055 mg/mL), and oxygen radical absorption capability assay (1.960 ± 0.381 mmol·TE/g). The final purified fraction U2-S2-I possessed the capability to protect plasmid DNA against the damage of hydroxyl radical and its effect was similar to that of the original hydrolysis product. It indicated that U2-S2-I might be the major active fraction of the hydrolysate. This study proved that bacterial extracellular proteases could be utilized in hydrolysis of a salmon byproduct. Compared with collagen, muscle proteins was an ideal material used as an enzymatic substrate to prepare antioxidant peptides.

Purification and Characterization of Antioxidant Peptides of Pseudosciaena crocea Protein Hydrolysates

Two peptides with antioxidant activity were isolated from Pseudosciaena crocea proteins. Pseudosciaena crocea muscle was hydrolyzed with neutral protease to obtain Pseudosciaena crocea protein hydrolysates (PCPH). After ultrafiltration through molecular weight cut-off membranes of 10, 5 and 3 kDa and assessment of free radical scavenging ability, the fraction (PCPH-IV) with the highest antioxidant activity was obtained. Several purification steps, i.e., ion exchange chromatography, gel filtration chromatography and reversed phase high performance liquid chromatography, were applied to further purify PCPH-IV. Two antioxidant peptides with the amino acid sequences Ser-Arg-Cys-His-Val and Pro-Glu-His-Trp were finally identified by LC-MS/MS.

Protective effect of gelatin peptides from pacific cod skin against photoaging by inhibiting the expression of MMPs via MAPK signaling pathway

Chronic exposure to ultraviolet (UV) irradiation causes skin photoaging. This study was undertaken to identify the anti-photoaging mechanisms of gelatin hydrolysate (CH) derived from pacific cod skin. Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) and ELISA assays were used to investigate the effects of CH on matrix metalloproteinases (MMPs) and the signaling pathways after UV irradiation by using a mice skin photoaging model. The average molecular weight of CH was 1200Da, and 273/1000 residues were hydrophobic, Gly-Pro and Gly-Leu sequences and Arg at C-terminus appeared frequently in CH. CH improved pathological changes of collagen fibers and significantly inhibited collagen content reduction in photoaging skin. Moreover, CH blocked the up-regulated expression of interstitial collagenase (MMP-1), stromelysin 1 (MMP-3), and gelatinase (MMP-9) in photoaging skin. Besides, CH suppressed the activities of MMPs by increasing the contents of tissue inhibitors of matrix metalloproteinases (TIMPs). CH significantly reduced the UV irradiation-dependent up-regulated phosphorylation of ERK and p38 in the mitogen-activated protein kinase (MAPK) signaling pathway. Furthermore, it inhibited the activation of activator protein 1 (AP-1) by down-regulating the mRNA level of c-Jun and c-Fos, which are the two transcription factors responsible for the regulation of MMPs expression. CH can effectively protect against UV irradiation-induced skin photoaging by inhibiting the expression and the activity of MMPs.

ACE-Inhibitory and Antioxidant Activities of Peptide Fragments Obtained from Tomato Processing By-Products Fermented Using Bacillus subtilis: Effect of Amino Acid Composition and Peptides Molecular Mass Distribution

The effects of amino acid composition and peptide molecular mass on ACE-inhibitory and antioxidant activities of protein fragments obtained from tomato waste fermented using Bacillus subtilis were evaluated. The addition of B. subtilis increased the relative amounts of aromatic and positively-charged amino acids which have been described to influence the biological activities of peptide fragments. IC₅₀ values of hydrolysates for ACE-inhibitory and 2, 2'-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities were found to be 1.5 and 8.2 mg/mL, respectively. Size-exclusion chromatography (SEC) pattern of the hydrolysate indicated the breakdown of parent proteins to smaller peptides with molecular weights mainly below 1400 Da. MALDI-TOF mass spectrometry analysis revealed that the highest ACE-inhibitory activity was due to peptides showing molecular mass range 500-800 Da, while the most active antioxidant peptides were found to be mainly at the two different peptide weight ranges 500-800 Da and 1200-1500 Da.

Anticancer activity of synthetic bis(indolyl)methane-ortho-biaryls against human cervical cancer (HeLa) cells

Bis(indolyl)methane appended biaryls were designed, synthesized and evaluated in human cervical cancer cell lines (HeLa) for their anticancer activities and compared against normal rat cardiac myoblasts (H9C2) cells. Compounds 1-12 were synthesized, with variations in one of the phenyl unit, in a single step by condensation of biaryl-2-carbaldehydes with indole in the presence of para-toluenesulfonic acid. Compound 1 exhibited a GI50 value of 11.00 ± 0.707 μM and the derivatives, compounds 4 and 11 showed a GI50 value of 8.33 ± 0.416 μM and 9.13 ± 0.177 μM respectively in HeLa cells and was found to be non-toxic to H9C2 cells up to 20 μM. Furthermore, compounds 1, 4 and 11 induced caspase dependent cellular apoptosis in a concentration-dependent manner, reduced mitochondrial membrane potential, inhibited the cell migration and downregulated the production of MMP-2 and MMP-9 in HeLa cells.

Antioxidant activities of bambara groundnut (Vigna subterranea) protein hydrolysates and their membrane ultrafiltration fractions

In this study, the bambara protein isolate (BPI) was digested with three proteases (alcalase, trypsin and pepsin), to produce bambara protein hydrolysates (BPHs).

Comparison of Neuroprotective and Cognition-Enhancing Properties of Hydrolysates from Soybean, Walnut, and Peanut Protein

Hydrolysates were prepared from soybean, walnut, and peanut protein by papain, respectively. Their amino acid compositions and molecular weight distributions, the effects of various hydrolysates on H2O2-induced injury PC12 cells, and cognition of mice were investigated, respectively. Results showed that the three hydrolysates were dominated by the peptides with 1–3 KDa with large amount of neurotrophic amino acids. All the hydrolysates exhibited much stronger inhibitory activity against H2O2-induced toxicity than cerebrolysin, and soy protein hydrolysate showed the highest activity. Moreover, the hydrolysates also could reduce the rate of nonviable apoptotic cells at the concentration of 2 mg/mL. The test of animal’s cognition indicated that three hydrolysates could present partly better effect of improving recurred memory ability of normal mice and consolidated memory ability of anisodine-treated mice than piracetam. Therefore, soybean, walnut, and peanut protein hydrolysates were recommended as a potential food raw material for prevention or treatment of neurodegenerative disorders.

Preventive effect of Nile tilapia hydrolysate against oxidative damage of HepG2 cells and DNA mediated by H2O2 and AAPH

Antioxidant activities of protein hydrolysate prepared from Nile tilapia protein isolate using Alcalase (HA), Alcalase followed by papain (HAPa) and their Sephadex G-25 fractions (FHA and FHAPa) were investigated in both chemical and cellular based models. Amongst all samples, FHAPa showed the highest chemical antioxidant activities, however it had no metal chelation activity. Cellular antioxidant ability of HA, HAPa and their fractions against H2O2 and AAPH induced oxidative damage of HepG2 cell and DNA were tested. When cells were pretreated with all hydrolysates or fractions at different concentrations (0.5-2 mg/mL) in the absence and presence of 50 μM Trolox, cell viability was in the range of 91.10-111.40 %. However, no difference in cell viability was observed among samples having various concentrations (P > 0.05). Cell reactive oxygen species (ROS) generation as mediated by H2O2 and AAPH decreased with treatment of hydrolysates or their fractions, especially in combination with 50 μM Trolox. FHAPa effectively inhibited H2O2 and peroxyl radical induced DNA scission in a dose dependent manner. Therefore, Nile tilapia protein hydrolysates could serve as a functional food ingredient.

Comparison of Antioxidant Activities of Hydrolysates of Domestic and Imported Skim Milk Powders Treated with Papain

Milk proteins have many potential sequences within their primary structure, each with a specific biological activity. In this study, we compared and investigated the bioactivities of hydrolysates of the domestic (A, B) and imported (C, D) skim milk powders generated using papain digestion. MALDI-TOF analysis revealed that all milk powder proteins were intact, indicating no autolysis. Electrophoretic analysis of hydrolysates showed papain treatment caused degradation of milk proteins into peptides of various size. The antioxidant activity of the hydrolysates, determined using 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and total phenolic contents (TPC) assays, increased with incubation times. In all skim milk powders, the antioxidant activities of hydrolysates were highest following 24 h papain treatment (TPC: A, 196.48 μM GE/L; B, 194.52 μM GE/L; C, 194.76 μM GE/L; D, 163.75 μM GE/L; ABTS: A, 75%; B, 72%; C, 72%; D, 57%). The number of peptide derived from skim milk powders, as determined by LC-MS/MS, was 308 for A, 283 for B, 208 for C, and 135 for D. Hydrolysate A had the highest antioxidant activity and the most potential antioxidant peptides amongst the four skim milk powder hydrolysates. A total of 4 β-lactoglobulin, 4 αs1-casein, and 56 β-casein peptide fragments were identified as potential antioxidant peptides in hydrolysate A by LC-MS/MS. These results suggest that domestic skim milk could have applications in various industries, i.e., in the development of functional foods.

Isolation and identification of antioxidant peptides from enzymatically hydrolyzed rice bran protein

Khao Dawk Mali 105 rice bran protein (RBP) was fractionated into albumin (12.5%), globulin (13.9%), glutelin (70.8%) and prolamine (2.9%). The native and denatured RBP fractions were hydrolyzed with papain and trypsin for 3h at optimum conditions. The RBP fractions and their hydrolysates were evaluated for their antioxidant activity by the Oxygen Radical Absorbance Capacity (ORAC) assay. The trypsin-hydrolyzed denatured albumin exhibited the highest antioxidant activity with an ORAC value of 4.07 μmol of Trolox equivalent (TE)/mg protein. This hydrolysate was separated by using RP-HPLC and three fractions with high antioxidant activity were examined by LTQ-FTICR ESI mass spectrometry. The MW of the peptides from these fractions were 800-2100 Da. and consisted of 6-21 amino acid residues. Most of the peptides from the fractions demonstrated typical characteristics of well-known antioxidant peptides. The results suggest that trypsin-hydrolyzed denatured rice bran albumin might be useful as a natural food antioxidant.

Seaweed polysaccharides (laminarin and fucoidan) as functional ingredients in pork meat: an evaluation of anti-oxidative potential, thermal stability and bioaccessibility

The anti-oxidative potential of laminarin (L), fucoidan (F) and an L/F seaweed extract was measured using the DPPH free radical scavenging assay, in 25% pork (longissimus thoracis et lumborum (LTL)) homogenates (TBARS) (3 and 6 mg/mL) and in horse heart oxymyoglobin (OxyMb) (0.1 and 1 mg/mL). The DPPH activity of fresh and cooked minced LTL containing L (100 mg/g; L100), F100 and L/F100,300, and bioaccessibility post in vitro digestion (L/F300), was assessed. Theoretical cellular uptake of antioxidant compounds was measured in a transwell Caco-2 cell model. Laminarin displayed no activity and fucoidan reduced lipid oxidation but catalysed OxyMb oxidation. Fucoidan activity was lowered by cooking while the L/F extract displayed moderate thermal stability. A decrease in DPPH antioxidant activity of 44.15% and 36.63%, after 4 and 20 h respectively, indicated theoretical uptake of L/F antioxidant compounds. Results highlight the potential use of seaweed extracts as functional ingredients in pork.