Li Guanghui, Xu Yunfeng, Wang Xin, Zhang Baigang, Shi Chao, Zhang Weisong, Xia Xiaodong
College of Food Science and Engineering, Northwest A&F University , Yangling, Shaanxi, China .
Foodborne Pathog Dis. 2014 Apr;11(4):313-9. doi: 10.1089/fpd.2013.1675. Epub 2014 Jan 21.
Pomegranate rind has been reported to inhibit several foodborne pathogens, and its antimicrobial activity has been attributed mainly to its tannin fraction. This study aimed to investigate the antimicrobial activity of the tannin-rich fraction from pomegranate rind (TFPR) against Listeria monocytogenes and its mechanism of action. The tannin-related components of TFPR were analyzed by high-performance liquid chromatography and liquid chromatography-mass spectrometry, and the minimum inhibitory concentration (MIC) of TFPR was determined using the agar dilution method. Extracellular potassium concentration, the release of cell constituents, intra- and extracellular ATP concentrations, membrane potential, and intracellular pH (pHin) were measured to elucidate a possible antibacterial mechanism. Punicalagin (64.2%, g/g) and ellagic acid (3.1%, g/g) were detected in TFPR, and the MICs of TFPR were determined to be 1.25-5.0 mg/mL for different L. monocytogenes strains. Treatment with TFPR induced a decrease of the intracellular ATP concentration, an increase of the extracellular concentrations of potassium and ATP, and the release of cell constituents. A reduction of pHin and cell membrane hyperpolarization were observed after treatment. Electron microscopic observations showed that the cell membrane structures of L. monocytogenes were apparently impaired by TFPR. It is concluded that TFPR could destroy the integrity of the cell membrane of L. monocytogenes, leading to a loss of cell homeostasis. These findings indicate that TFPR has the potential to be used as a food preservative in order to control L. monocytogenes contamination in food and reduce the risk of listeriosis.
据报道，石榴皮可抑制多种食源性病原体，其抗菌活性主要归因于其单宁部分。本研究旨在探讨石榴皮富含单宁部分（TFPR）对单核细胞增生李斯特菌的抗菌活性及其作用机制。采用高效液相色谱和液相色谱 - 质谱联用技术分析TFPR中与单宁相关的成分，并采用琼脂稀释法测定TFPR的最低抑菌浓度（MIC）。通过测量细胞外钾离子浓度、细胞成分释放、细胞内和细胞外ATP浓度、膜电位以及细胞内pH值（pHin）来阐明可能的抗菌机制。在TFPR中检测到了安石榴苷（64.2%，g/g）和鞣花酸（3.1%，g/g），不同单核细胞增生李斯特菌菌株的TFPR MIC测定值为1.25 - 5.0 mg/mL。用TFPR处理导致细胞内ATP浓度降低、细胞外钾离子和ATP浓度升高以及细胞成分释放。处理后观察到pHin降低和细胞膜超极化。电子显微镜观察表明，TFPR明显损害了单核细胞增生李斯特菌的细胞膜结构。得出的结论是，TFPR可破坏单核细胞增生李斯特菌细胞膜的完整性，导致细胞内稳态丧失。这些发现表明，TFPR有潜力用作食品防腐剂，以控制食品中单核细胞增生李斯特菌的污染并降低李斯特菌病的风险。
