In this study, an antioxidant peptide was purified from the protein hydrolysate of germinated chickpea by Sephadex column chromatography, and its antioxidant activities were evaluated by determining free radical scavenging capacity, reducing power, lipid oxidation inhibitory effect and protective effect against free radical-induced damage to proteins and DNA. The purified peptide was identified and synthesized to verify its antioxidant activities, and the safety of the synthetic peptide was predicted. The results showed that the antioxidant peptide had good free radical scavenging ability and reducing power, significantly inhibited the autooxidation of linoleic acid, and protected against protein and DNA damage induced by free radicals. It was predicted that the synthetic peptide had no toxicity or allergenicity. In conclusion, the protein hydrolysate of germinated chickpea has antioxidant capacity and can be used to prepare antioxidant peptides, which will improve the utilization value of chickpea.

In this study, the total phenol and flavonoid contents of the ethanol extract of green walnut husks were determined as (21.71±0.98) and (22.16±0.45) mg/g, respectively. Using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) and high performance liquid chromatography (HPLC), nine major compounds in the extract were identified including quercitrin, avicularin, astragalin, hyperoside, isoquercetin, quercetin, caffeic acid, ferulic acid and juglone. The extract had a protective effect against 2,2’-azobis-2-methyl-propanimidamide dihhydrochloride (AAPH)-induced oxidative damage to biological macromolecules. The extract at 1 mg/mL had a significant protective effect against oxidative damage to bovine serum albumin (BSA), and at 0.5 mg/mL, it could protect plasmid DNA from oxidative damage. The extracts had antibacterial activity against Escherichia coli, which could increase the permeability of the bacterial cell membrane and destroy its integrity, thereby resulting in the leakage of intracellular nucleic acid and proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results showed that the damage to cellular proteins could be another antibacterial mechanism of the extract. In addition, the extract inhibited the respiration of E. coli, and the percent increase in respiration rate with the extract alone compared to that with its combination with trisodium phosphate was the lowest. The extract significantly reduced the activity of glucose-6-phosphate dehydrogenase. Therefore, it can be inferred that the extract exerts an antibacterial effect mainly by participating in regulating the respiratory metabolism of the pentose phosphate pathway.

The antibacterial activity and mechanism of juglone from walnut green husk against Escherichia coli were studied. E. coli was treated with juglone from walnut green husk in different concentrations. The minimum inhibitory concentration (MIC) of juglone was determined, and its effect on the growth curve, cell membrane relative conductivity, fluorescence emission spectrum, biofilm formation, cell viability, protein formation and genomic DNA and RNA synthesis of E. coli were investigated. The results showed that juglone had effective antibacterial activity against E. coli with an MIC value of 0.0625 mg/mL. The relative conductivity of E. coli cell membrane increased after treatment with different concentrations of juglone, indicating that juglone destroyed the integrity of the cell membrane and increased the permeability. The results of fluorescence emission spectroscopy showed that juglone was able to interact with membrane proteins to change the membrane structure of E. coli cells. The results of crystal violet and resazurin staining showed that juglone could weaken the respiration of E. coli by inhibiting the formation of E. coli biofilms, thereby inhibiting its viability. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and E. coli genome synthesis analysis showed that juglone inhibited the expression of protein, DNA and RNA in E. coli. Through molecular docking, it was found that juglone can bind to the grooves of genomic DNA, thereby changing its secondary structure and morphology. In summary, juglone has a good inhibitory effect on E. coli, and can therefore be used as a natural antibacterial agent in the prevention and control of foodborne E. coli.