Antimicrobial intermediates of the general phenylpropanoid and lignin specific pathways.

The minimum inhibitory concentration (MIC) of the major intermediates of the general phenylpropanoid and lignin specific pathways of plants were determined employing a range of yeasts and bacteria. Of the three main classes of compounds tested, the hydroxycinnamaldehydes were the most effective, possessing notable antifungal and antibacterial activity. Determination of the minimum killing concentration (MKC) of the hydroxycinnamaldehydes revealed MIC/MKC ratios suggesting these compounds to be fungicidal, but not bactericidal, in their mode of action. In contrast, the hydroxycinnamic acids and hydroxycinnamyl alcohols possessed little antimicrobial activity, with the exception of the hydroxycinnamic acids, which were antibacterial.