Purpose: The objective of this study was to evaluate the antibacterial characteristics and mechanisms of anthocyanins extracted from wild blueberries (Vaccinium angustifolium) against four foodborne pathogens.
Methods: Wild blueberries were extracted using the methanol extraction method. The fraction of anthocyanins was separated from blueberry extract by the C-18 column. Listeria monocytogenes (NO.12), Staphyloccocus aureus (AB91093), Salmonella Enteritidis (CMCC50041), and Vibrio parahaemolyticus (VP6) were used for investigating the antibacterial effects of anthocyanins. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of anthocyanins were determined by a twofold serial dilution method. The ability of anthocyanins to alter the membrane integrity of pathogens were visualized using scanning electron microscopy (SEM). After anthocyanins treatments, the metabolism of four pathogens was assessed by the value of OD630. The total protein content, ATP enzyme, and AKP enzyme were measured with protein assay kits.
Results: The MBCs of anthocyanins against L. monocytogenes, S. aureus, S. Enteritidis, V. parahaemolyticus were 0.53 mg/mL, 0.27 mg/mL, 0.53 mg/mL, and 0.13 mg/mL, respectively. SEM confirmed that anthocyanins destroyed the cell membrane of the four bacteria. When foodborne pathogens were treated with anthocyanins for 2 h, total protein content decreased and the enzyme activity of AKP and ATP decreased by 54.3% and 69.7%, respectively. With increasing concentration of anthocyanins, the value of OD630 distinctly decreased, indicating bacterial metabolism was decreased. This may affect the energy transfer of bacteria and inhibit bacterial growth and reproduction.
Significance: This study demonstrated that anthocyanins affected bacterial metabolism and reduced the bacterial cell activity through destroying the cell membrane and the growth condition of bacteria. Wild blueberry anthocyanins have potential applications in preventive medicine and food safety.