SYNTHESIS AND ANTIBACTERIAL ACTIVITIES EVALUATION OF WATER-SOLUBLE CAFFEIC ACID AMMONIUM SALTS

Abstract

A series of water-soluble caffeic acid ammonium salts (compounds 1–28) were synthesized by acid-base neutralization. Except compound 21, all the compounds were first reported. The chemical structures of these compounds were confirmed by means of 1H NMR, ESI MS and elemental analyses. All of the compounds were assayed for antibacterial (Bacillus subtilis ATCC 6633, Escherichia coli ATCC 35218, Pseudomonas fluorescens ATCC 13525 and Staphylococcus aureus ATCC 6538) activities by MTT method. Compounds benzenaminium (E)-3-(3,4-dihydroxyphenyl)acrylate (6), dibutylammonium (E)-3-(3,4-dihydroxyphenyl)acrylate (24) and triethylammonium (E)-3-(3,4-dihydroxyphenyl)acrylate (27) showed considerable antibacterial activities. Generally, straight aliphatic ammonium salts were more powerful than branched aliphatic ammonium salts or aromatic ones, and tertiary ammonium salts had higher antibacterial activity than primary and secondary ammonium salts