Antimicrobial properties of green tea catechins.

Extracts of leaves from the tea plant Camellia sinensis contain polyphenolic components with activity against a wide spectrum of microbes. Studies conducted over the last 20 years have shown that the green tea polyphenolic catechins, in particular (-)-epigallocatechin gallate (EGCg) and (-)-epicatechin gallate (ECg), can inhibit the growth of a wide range of Gram-positive and Gram-negative bacterial species with moderate potency. Evidence is emerging that these molecules may be useful in the control of common oral infections, such as dental caries and periodontal disease. Sub-inhibitory concentrations of EGCg and ECg can suppress the expression of bacterial virulence factors and can reverse the resistance of the opportunistic pathogen Staphylococcus aureus to beta-lactam antibiotics. For example, relatively low concentrations of ECg can sensitize methicillin-resistant S. aureus (MRSA) clinical isolates to levels of oxacillin that can be readily achieved in clinical practice. Catechin gallates such as ECg intercalate into phopsholipid bilayers and it is likely that they affect both virulence and antibiotic resistance by perturbing the function of key processes associated with the bacterial cytoplasmic membrane.