Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/13/2005
Publication Date: 1/10/2006
Citation: Friedman, M., Henika, P.R., Levin, C.E., Mandrell, R.E. 2006. Antibiotic activities of green tea catechins and green tea extracts at nanomolar levels against the foodborne pathogen bacillus cereus. Journal of Food Protection. 69:100-107. Interpretive Summary: As part of an effort designed to develop antimicrobial food formulations that will protect both the food and the consumer against pathogenic bacteria and viruses, we evaluated the bactericidal activities of eleven of polyphenolic catechins present in green teas and of four green tea extracts against the foodborne pathogen Bacillus cereus reported to contaminate baked goods, carrots, meat, milk products, rice, sauces, soups, sprouts, and zucchini. The results show that three of the catechins exhibited exceptional bactericidal activities at very low levels in the nanomolar range. They were more active than medicinal antibiotics such as tetracycline and vancomycin. Future studies should define their antimicrobial effectiveness in foods and feeds and as disinfectants of surfaces of non-food items such as cutting boards.
Technical Abstract: A bactericidal assay was used to evaluate dose-response of a dilution series (0.067%, 0.0067%, 0.00067%, and 0.000067%, w/v) in a phosphate-saline pH 7.0 buffer of carvacrol and thymol, 11 green tea phenolic compounds (catechins), 3 commercial green tea extracts, 1 tea prepared from green tea leaves, and 5 medicinal antibiotics in terms of the % (w/v) of sample that killed 50% of the foodborne pathogen Bacillus cereus (BA50) incubated at 21 ºC for 3, 15, and 30 min. Antimicrobial activities of the catechins, but not of the antibiotics, increased with incubation times. Carvacrol and thymol had similar BA50 values of 0.022 and 0.025, respectively. Six of the eleven catechins were active in the assay, with average 30 min BA50 values ranging from 0.031 for (')-gallocatechin to 0.0000048% (48 ng/mL) for (')-epicatechin gallate, a 6,500 variation from least to most active catechin. Activities of the catechins were in the following order: (')-epicatechin gallate > epigallocatechin-3-gallate = (')-gallocatechin gallate > (')-catechin gallate >> (')-gallocatechin = (')-epigallocatechin. The green tea extracts and the green tea were also highly active. The BA50 values of the antibiotics ranged from 0.0054 to 0.000025, with activities in the following order: rifampicin > vancomycin > clindamycin > tetracycline > chloramphenicol. Some catechins were more active than some of the antibiotics. Possible mechanisms of the antibacterial effects and the significance of the results for food safety and human health are discussed.