Anti-Staphylococcus aureus activity and oxacillin resistance modulating capacity of 3-O-acyl-catechins

Epicatechin gallate (ECg), a component of green tea with weak activity against Staphylococcus aureus, reduces oxacillin resistance in methicillin-resistant S. aureus at concentrations below the MIC. Because catechins bind to artificial lipid bilayers, we investigated whether the anti-staphylococcal activity of catechins could be improved by increasing their capacity to interact with the cytoplasmic membrane. Substitution of the gallate group of ECg with 3-O-acyl chains of varying lengths (C(4)-C(18)) led to enhanced anti-staphylococcal activity with chain lengths of C(8) (octanoyl) and C(10) (decanoyl). 3-O-octanoyl catechin was bactericidal against MRSA as the result of membrane damage. 3-O-acyl catechins tested at a 1/4 MIC did not reduce the oxacillin MIC greater than two-fold. 3-O-acyl catechins warrant further investigation as anti-staphylococcal agents.