Antimicrobial intermediates of the general phenylpropanoid and lignin specific pathways

The minimum inhibitory concentration (MIC) of the major intermediates of th e general phenylpropanoid and lignin specific pathways of plants were deter mined employing a range of yeasts and bacteria. Of the three main classes o f compounds tested, the hydroxycinnamaldehydes were the most effective, pos sessing 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 bacter icidal, 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. (C) 2000 Elsevier Science Ltd. All rights reserved.