Antibacterial action on pathogenic bacterial spore by green tea catechins

Antibacterial effects of catechins, the major green tea polyphenols, were studied using Clostridium and Bacillus spores. Incubation with crude catechins decreased the number of C botulinum and C butyricum spores but not B cereus spores. Furthermore, the effects of six catechin derivatives on spores were investigated. (-)-Epicatechin gallate (ECg), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCg) and (+)-gallocatechin gallate (GCg) were more effective in decreasing C botulinum and C butyricum spore numbers than (+)-catechin (C) and (-)-epicatechin (EC). The vegetative growth of C botulinum and B cereus was inhibited by crude extracts of the catechins. Specifically, purified GCg and EGCg inhibited the vegetative growth of C botulinum and B cereus. The inhibitory effect of ECg on B cereus was similar to that of GCg. However, toxin-production by B cereus was not inhibited by catechin. Damage to the membrane of C butyricum spores by catechin derivatives was shown using fluorescent microscopy. This study shows that low concentrations of catechins, although requiring a long exposure time, inhibited the growth of bacterial spores. However, the effects of the purified derivatives of the catechins were not the same and GCg and EGCg were found to be the most potent. Spores that are generally resistant to many disinfectants were sensitive to catechins.