•Red rice polyphenols (RRP) inhibited pancreatic α-Amylase (PA) activity.•Inhibition mode of RRP on PA was reversible.•Molecular docking was used to speculate the inhibition mechanism of RRP on PA.This study sought to investigate the possible inhibition mechanism of red rice polyphenols (RRP) on pancreatic α-amylase (PA) activity. RRP showed strong inhibition against PA activity and the half-inhibitory concentration (IC50) value was 3.61 μg/mL. The fluorescence quenching of PA by RRP was a combination of static quenching and dynamic quenching. RRP could aggregate with PA and the physiochemical properties of the aggregates were closely related to the concentration of RRP. Kinetic analysis suggested that the inhibition mode of RRP on PA was reversible inhibition, which was a mixing of competitive inhibition and noncompetitive inhibition. Molecular docking speculated that RRP could form hydrogen bonds with PA by binding to the catalytic active sites (ASP197, GLU233 and ASP300) and the microenvironments of TRP58 and TRP59 were altered, thus inhibiting PA activity.

Antifreeze proteins (AFPs) were extracted from cold-acclimated oat by vacuum infiltration–centrifugation. Ammonium precipitation, ion exchange, and size-exclusion chromatography were used successively to purify the oat AFPs (AsAFPs), and the proteins were identified using matrix-assisted laser desorption/ionization time of flight tandem mass spectrometry. The results showed that an ammonium-sulfate saturation of 50–100 % was optimal for supernatant precipitation. After purification, AsAFP was found to have achieved an electrophoretic purity and its thermal-hysteresis activity was measured at 1.24 °C (15 mg ml−1). The mass fingerprinting and sequencing results indicated the homology of AsAFP and endochitinase. Recrystallization and melting resistance of ice cream were improved by AsAFP (0.1 %). Moreover, the addition of AsAFP (0.1 %) in ice cream increased the glass transition temperature (Tg) from −29.14 to −27.74 °C.

•The protein hydrolysate of anchovy cooking wastewater (ACWWPH) was antibacterial.•The liposomes were constructed from S. aureus membrane lipids.•An antimicrobial peptide was targeted separated from ACWWPH by equilibrium dialysis.•The peptide induced the change in cell surface hydrophobicity.•The peptide had membrane-permeable action.Anchovy (Engraulis japonicus) cooking wastewater (ACWW) is a by-product resulted from the production of boiled–dried anchovies in the seafood processing industry. In this study, the protein hydrolysate of ACWW (ACWWPH) was found to have antimicrobial activity after enzymatic hydrolysis with Protamex. For the targeted screening of antibacterial peptides, liposomes constructed from Staphylococcus aureus membrane lipids were used in an equilibrium dialysis system. The hydrolysate was further purified by liposome equilibrium dialysis combined with high performance liquid chromatography. The purified antimicrobial peptide (ACWWP1) was determined to be GLSRLFTALK, with a molecular weight of 1104.6622 Da. The peptide exhibited no haemolytic activity up to a concentration of 512 μg/ml. It displayed a dose-dependent bactericidal effect in reconstituted milk. The change in cell surface hydrophobicity and membrane-permeable action of the purified ACWWP1 may have contributed to the antibacterial effect. This study suggests that liposome equilibrium dialysis can be used for the targeted screening of antimicrobial peptides.

•LF-NMRI was used to monitor water migration of barley grain during infiltration.•Infiltration–centrifugation was demonstrated to be targeted in BaAFPs extraction.•BaAFPs was demonstrated to be accumulate after cold-acclimation.•BaAFP-I at an electrophoresis level was obtained after a series of purification.•BaAFP-I was identified to be an homology of alpha-amylase inhibitor BDAI-1.Antifreeze proteins from cold-acclimated malting barley were extracted by infiltration–centrifugation. The infiltration time was optimised, and its extraction effect was evaluated. The effect of cold acclimation on the accumulation of barley antifreeze proteins (BaAFPs) was assessed by comparing the thermal hysteresis activities (THA) of proteins extracted from both cold acclimated and non-cold acclimated barley grain. Ultra-filtration, ammonium precipitation and column chromatography were used successively to purify the BaAFPs, and MALDI-TOF-MS/MS was used for protein identification. The results showed that infiltration–centrifugation was more targeted than the traditional method, and 10 h was the optimal infiltration time. THA was observed only after cold acclimation implied that AFPs only began to accumulate after cold acclimation. After purification, BaAFP-I was obtained at an electrophoresis level and its THA was 1.04 °C (18.0 mg ml−1). The mass fingerprinting and sequencing results indicated the homology of the BaAFP-I to alpha-amylase inhibitor BDAI-1 (Hordeum vulgare).

An efficient immobilized bacterial membrane liposome chromatography method was used to screen potential antimicrobial peptides from boiled-dried anchovies. A novel cationic antimicrobial peptide (Apep10) was successfully isolated by one-step chromatography. The sequence of Apep10 was identified as GLARCLAGTL by matrix-assisted laser desorption/ionization quadrupole time-of-flight tandem mass spectrometry (MALDI-Q-TOF MS). The antimicrobial activity assessment indicated that Apep10 inhibited the growth of the reference bacteria (Escherichia coli, Shigella dysenteriae, Pseudomonas aeruginosa, Salmonella typhimurium, Staphylococcus aureus, Bacillus subtilis, and Streptococcus pneumoniae), with minimal inhibitory concentration (MIC) values ranging from 8 to 64 μg/mL. Almost no cytotoxicity against mouse erythrocytes was observed at concentrations below 20 μg/mL. Nucleotide leakage induced by Apep10 showed that the peptide exhibited permeable activity on the cytoplasmic membrane. Alterations in morphology were observed by scanning electronic microscopy (SEM). Membrane disruption was confirmed by confocal laser scanning microscopy (CLSM) with propidium iodide (PI). The results demonstrate that immobilized bacterial membrane liposome chromatography is a straightforward technique for screening unknown antimicrobial peptides with cell-membrane-interacting activities from boiled-dried anchovies.

Different methods of defatting have a great impact on toxic, antinutritional and nutritive factors in the oilseed meals. In order to find the most suitable methods of defatting for Jatropha curcas seed meals, the Jatropha curcas L. seed meals, defatted by Soxhlet extraction and screw-press were characterized for their toxic, anti-nutritional and nutrient factors in this study. The toxins (phorbolesters, 3.1 and 2.9 mg/g) and some anti-nutritional factors (saponins, 2.9 and 2.6%; phytates, 11.1 and 11.6%) in meals obtained by the two defatting methods were present at high concentrations. However, the trypsin inhibitors activity (TIA) and lectin (2.7 mg/g and 1.5 mg/ml) in the screw-pressed meal were significantly lower, due to the high temperature (120 °C) used in this defatting process. From nutritional side, the values of crude protein (CP), buffer-soluble nitrogen, non-protein nitrogen, pepsin insoluble nitrogen, in vitro protein digestibility (IVPD), as well as essential amino acid index (EAAI), biological value (BV), nutritional index (NI) and protein-digestibility-corrected amino acid score (PDCAAS) of the meal obtained by Soxhlet extraction were better than the screw-pressed meal. However, taking practical application into account, from detoxification side, screw-pressed meal is better for detoxification.

Antimicrobial peptides are of greatest potential as a new group of antibiotics. Enzymatic hydrolysis was performed using flavourzyme, pepsin, trypsin, neutrase, papain and alcalase to obtain antimicrobial peptides from ovalbumin. Pepsin hydrolysate exhibited the highest antimicrobial activity compared with other fractions. To purify and characterize antimicrobial peptide, an immobilized liposome-binding extraction method was developed, in which the liposome was regarded as a mimic biomembrane system. The immobilized liposome stationary phase was prepared, and the maximum adsorption capacity and Langmuir constant were 81.30 μM/g and 8.19 mL/mg, respectively. Four fragments were simultaneously predicted by the comparison between reverse-phase high-performance liquid chromatography chromatograms of pepsin hydrolysate before and after interaction with immobilized liposome membrane. A novel cationic antimicrobial peptide named Opep2 was sequenced as RVASMASEKMKI. In addition, antimicrobial mode experiments showed that Opep2 interacted with cell wall membrane and caused potassium efflux, nucleotide leakage and ultimately cell death. Because of the high efficiency and procedural simplicity, the immobilized liposome-binding extraction method could be more efficient for the screening of antimicrobial peptides than conventional methods, which provides scientific references for antimicrobial peptide production.

To understand the details of the permeation pathways of antimicrobial peptide JCpep8, the antimicrobial processes were investigated step by step in this paper. First, the characterization of the initial binding process was explored by introducing the living Staphylococcus aureus cells (LSACs) into electrophoretic buffer used as pseudo-stationary phase in capillary electrochromatography (CEC), and the thermodynamic parameters were determined. The binding constants at 298, 303, and 309 K were 7.40 × 1011, 1.43 × 1012, and 2.6 × 1012 M–1, respectively, which indicated the evident interaction between JCpep8 and LSACs. This binding process was spontaneous. Both the electrostatic force and hydrophobic effect play major roles in this binding process. Second, antibacterial activity kinetics and outer membrane and inner membrane disruption assays were investigated. Data indicated that JCpep8 killed microbes principally by breaking their cell wall and membrane, followed by cell lysis. The results were confirmed by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). In summary, JCpep8 kills microbes mainly by wall-/membrane-targeting pore-forming mechanisms.

A novel method named cell membrane affinity chromatography was used to screen antimicrobial peptides from Jatropha curcas. A cationic antimicrobial peptide (KVFLGLK, JCpep7) was successfully isolated and identified. Antimicrobial assays indicated that JCpep7 was active against the tested microorganisms (Salmonella typhimurium ATCC 50013, Shigella dysenteriae ATCC 51302, Pseudomonas aeruginosa ATCC 27553, Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 23631, and Streptococcus pneumoniae ATCC 49619) with minimal inhibitory concentration (MIC) values ranging from 24 to 64 μg/mL. The antimicrobial mechanisms based on Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) techniques showed that JCpep7 killed microbes principally via breaking of their cell walls and membranes, followed by cell lysis. The results indicated that cell membrane affinity chromatography could be a promising approach for high-throughput screening of antimicrobial peptides from J. curcas.

The Jatropha curcas meal was detoxified by different methods, and the effect of detoxification was evaluated in this study. The method that hydrolysis of enzymes (cellulase plus pectinase) followed by washing with ethanol (65%) had a significant (p < 0.05) effect on the toxin, antinutritional components, and nutritional quality of proteins. After this treatment, the phorbolesters (PEs) were decreased by 100%. The antinutritional components (phytates, tannins, saponins, protease inhibitor, and lectin activities) were decreased to tolerable levels, which were lower than those in soybean meal. The crude protein in detoxified meal was 74.68%, and the total content of amino acids was 66.87 g/100 g of dry matter. The in vitro protein digestibility (IVPD) increased from 82.14 to 92.37%. The pepsin-insoluble nitrogen was only 4.57% of the total nitrogen, and about 90% of the protein was true protein. The protein-digestibility-corrected amino acid score (PDCAAS) of the meal was 0.75. The results showed that this treatment was a promising way to detoxify J. curcas meal, and the nutritional quality of detoxified meal can be simultaneously enriched and improved.

The interaction between antimicrobial peptide (JCpep7) and the living Staphylococcus aureuscells (LSACs) used as pseudo-stationary phase in Capillary Electrochromatography (CEC) was investigated in this paper. The binding constants at 298, 303 and 309 K was 3.85 × 1012 M−1, 5.04 × 1012 M−1 and 6.73 × 1012 M−1, which indicated the evident interaction between JCpep7 and LSACs. The positive enthalpy change (ΔH) and entropy change (ΔS) values showed that hydrophobic effect played a major role in the binding process. Furthermore, to better understand the binding process between JCpep7 and LSACs, conformational changes of JCpep7 when it bound to the living bacteria was also studied by fluorescence spectrum and the results were consistent with those obtained by CEC.

The defatted rice endosperm protein (REP) was, respectively, digested by five different protease treatments (Alcalase, Chymotrypsin, Neutrase, Papain and Flavorase), and Neutrase appears to be the most desirable for producing high quality antioxidant peptides from REP. Specially, the DPPH and hydroxyl radical scavenging activities of NHREP were higher than its superoxide radical scavenging activity, and the percentage inhibition of autooxidation of NHREP (80.09%) was similar to that of α-tocopherol (86.59%) on day 5. Furthermore, NHREP was purified consecutively, and the antioxidant peptides were identified to be Phe-Arg-Asp-Glu-His-Lys-Lys (FRDEHKK, 959.5 Da) and Lys-His-Asp-Arg-Gly-Asp-Glu-Phe (1002.5 Da) by MALDI-TOF/TOF MS/MS. Lastly, FRDEHKK was chemically synthesised. It significantly inhibited lipid peroxidation in an linoleic acid emulsion system more effectively than α-tocopherol, and enhanced the viability of t-BHP induced cytotoxicity up to 74.38% (for MRC-5) and 78.39% (for RAW264.7) at 80 μg/ml. Conclusively, it was feasible to produce natural antioxidants from REP.

The defatted rice endosperm protein (REP) was digested using five different proteases (Alcalase, Chymotrypsin, Neutrase, Papain, and Flavorase) to produce the antioxidative peptide. The degree of hydrolysis of REP by Neutrase (20.00%) was slightly lower than that of Chymotrypsin, but higher than those of other enzymes. The Neutrase hydrolysate from rice endosperm protein (NHREP) took on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity similar to α-tocopherol. Also, the reaction condition of Neutrase hydrolysis was moderate (pH of 7.0 and temperature of 37 °C). Therefore, Neutrase was chosen to be the optimum enzyme for producing the antioxidative peptide from REP. In succession, the antioxidant activities of NHREP were further evaluated. The median effective concentration (EC50) value of NHREP for hydroxyl radical scavenging activity was 2.0 mg/mL, while its superoxide radical scavenging activity did not surpassed 50% even at 6 mg/mL. The percentage inhibition of autooxidation in linoleic acid system by NHREP was 82.09%, similar to that of α-tocopherol (86.59%) on day 5 at the same concentration. NHREP displayed 89.15% chelating effect on ferrous ion at a concentration of 1000 μg/mL, and a high correlation was also observed between the reducing power and antioxidant activity of NHREP (r2 = 0.99678). Consequently, NHREP was purified and identified, and the sequence determination by MALDI-TOF/TOF MS/MS revealed that the active constituent contained eight amino acids in its sequence (Lys-His-Asn-Arg-Gly-Asp-Glu-Phe), with the molecular mass of 1002.5217 Da. After sequence interpretation and database searching, the MS/MS spectrum was matched to glutelin protein f (460–465).

•Four components of different oats were determined and analyzed.•Fatty acid compositions were selected to represent the information of oat.•The main fatty acid compositions of oats were determined.•The standard fingerprint was established and 11 fatty acids were selected.•The established fingerprint has high precision, repeatability and stability.Oat samples of different varieties were collected from various habitats for the determination of avenacoside, β-glucan and fatty contents. The variation coefficients of the three components were 12.13%, 20.79% and 22.46%, respectively. Thus, those three indicators cannot represent the information of all samples, and are not suitable for evaluating the quality of oat raw materials and products. Fatty acid profiles were analyzed using gas chromatography combined with principal component analysis (PCA) and cluster analysis. Fourteen leather oat varieties were distinguished through a PCA scores scatterplot. Forty-six naked oat varieties were selected by cluster analysis and eleven characteristic peaks in these naked oats were identified. Finally, accurate fatty acid standard fingerprints of naked oats were constructed. The results of methodological indicated high precision, reproducibility and stability, in line with fingerprint testing requirements. This study fills the knowledge gap for naked oat fingerprint information, expands the grain fatty acid database, and lays the foundations of a grain nutritional liposome identification technology system.

The interaction between antimicrobial peptide (JCpep7) and the living Staphylococcus aureuscells (LSACs) used as pseudo-stationary phase in Capillary Electrochromatography (CEC) was investigated in this paper. The binding constants at 298, 303 and 309 K was 3.85 × 1012 M−1, 5.04 × 1012 M−1 and 6.73 × 1012 M−1, which indicated the evident interaction between JCpep7 and LSACs. The positive enthalpy change (ΔH) and entropy change (ΔS) values showed that hydrophobic effect played a major role in the binding process. Furthermore, to better understand the binding process between JCpep7 and LSACs, conformational changes of JCpep7 when it bound to the living bacteria was also studied by fluorescence spectrum and the results were consistent with those obtained by CEC.