Si Weiduo, Gong Joshua, Tsao Rong, Kalab Milosh, Yang Raymond, Yin Yulong
Food Research Program, Agriculture and Agri-Food Canada, Guelph, Ont. N1G 5C9, Canada.
J Chromatogr A. 2006 Sep 1;1125(2):204-10. doi: 10.1016/j.chroma.2006.05.061. Epub 2006 Jun 23.
The Chinese green tea extract was found to strongly inhibit the growth of major food-borne pathogens, Escherichia coli O157:H7, Salmonella Typhimurium DT104, Listeria monocytogenes, Staphylococcus aureus, and a diarrhoea food-poisoning pathogen Bacillus cereus, by 44-100% with the highest activity found against S. aureus and lowest against E. coli O157:H7. A bioassay-guided fractionation technique was used for identifying the principal active component. A simple and efficient reversed-phase high-speed counter-current chromatography (HSCCC) method was developed for the separation and purification of four bioactive polyphenol compounds, epicatechin gallate (ECG), epigallocatechin gallate (EGCG), epicatechin (EC), and caffeine (CN). The structures of these polyphenols were confirmed with mass spectrometry. Among the four compounds, ECG and EGCG were the most active, particularly EGCG against S. aureus. EGCG had the lowest MIC90 values against S. aureus (MSSA) (58 mg/L) and its methicilin-resistant S. aureus (MRSA) (37 mg/L). Scanning electron microscopy (SEM) studies showed that these two compounds altered bacterial cell morphology, which might have resulted from disturbed cell division. This study demonstrated a direct link between the antimicrobial activity of tea and its specific polyphenolic compositions. The activity of tea polyphenols, particularly EGCG on antibiotics-resistant strains of S. aureus, suggests that these compounds are potential natural alternatives for the control of bovine mastitis and food poisoning caused by S. aureus.
研究发现，中国绿茶提取物能强烈抑制主要食源性病原体的生长，包括大肠杆菌O157:H7、鼠伤寒沙门氏菌DT104、单核细胞增生李斯特菌、金黄色葡萄球菌以及一种引起腹泻性食物中毒的病原体蜡样芽孢杆菌，抑制率为44%-100%，其中对金黄色葡萄球菌的活性最高，对大肠杆菌O157:H7的活性最低。采用生物测定导向的分级分离技术来鉴定主要活性成分。开发了一种简单高效的反相高速逆流色谱（HSCCC）方法，用于分离和纯化四种生物活性多酚化合物，即表儿茶素没食子酸酯（ECG）、表没食子儿茶素没食子酸酯（EGCG）、表儿茶素（EC）和咖啡因（CN）。通过质谱确认了这些多酚的结构。在这四种化合物中，ECG和EGCG活性最强，尤其是EGCG对金黄色葡萄球菌的活性最强。EGCG对金黄色葡萄球菌（MSSA）的最低MIC90值为58 mg/L，对耐甲氧西林金黄色葡萄球菌（MRSA）的最低MIC90值为37 mg/L。扫描电子显微镜（SEM）研究表明，这两种化合物改变了细菌细胞形态，这可能是由于细胞分裂受干扰所致。本研究证明了茶的抗菌活性与其特定的多酚成分之间存在直接联系。茶多酚，尤其是EGCG对耐抗生素金黄色葡萄球菌菌株的活性表明，这些化合物是控制由金黄色葡萄球菌引起的牛乳腺炎和食物中毒的潜在天然替代品。
