Antimicrobial activity of 3-O-acyl-(-)-epicatechin and 3-O-acyl-(+)-catechin derivatives

As an exploratory investigation of antimicrobial promoting compounds, 3- O-acyl-(-)-epicatechins and 3- O-acyl-(+)-catechins possessing various aromatic groups and aliphatic chains of varying length from C4 to C16 for increasing lipophilicity were synthesized and tested for antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi. The (-)-epicatechin and (+)-catechin derivatives comprised of aromatic groups increased activity and derivatives with acyl chain groups of carbon atoms in the close vicinity of C8 to C10 showed strong antimicrobial activity (MIC = 2 - 8 microg/ml) against Gram-positive bacteria and weak activity against fungi. However, the activity decreased when the carbon chain length of the substituents was too short (C4 to C6) or too long (C16). These results suggest that the presence of lipophilic substituents with moderate sizes might be crucial for the optimal antimicrobial activity.