Synthesis and antimicrobial activities of 3-O-alkyl analogues of (+)-catechin: improvement of stability and proposed action mechanism.

We report here the synthesis and biological properties of 3-O-alkyl analogues of (+)-catechin (5), which itself is one of the major natural polyphenols found in green tea and has several physiological activities. Starting from 5, a series of 3-O-alkyl-(+)-catechin derivatives were investigated as potent antimicrobial agents. The presence of an alkyl chain rather than acyl on 3-O- showed an increase in antimicrobial activity which may be due to stability in standard culture condition. The most promising compound is 8e, 3-O-decyl analogue, with the MIC of 0.5-2, 32-128 and 2-4 microg/mL against Gram-positive bacteria, Gram-negative bacteria and human pathogenic fungi, respectively. Regarding action mechanism, the antimicrobial activity is possibly due to the lipophilicity and disrupting ability of the analogues to the liposome membrane.