Natural cinnamic acids, synthetic derivatives and hybrids with antimicrobial activity

Abstract

Antimicrobial natural preparations involving cinnamon, storax and propolis have been long used topically for treating infections. Cinnamic acids and related molecules are partly responsible for the therapeutic effects observed in these preparations. Most of the cinnamic acids, their esters, amides, aldehydes and alcohols, show significant growth inhibition against one or several bacterial and fungal species. Of particular interest is the potent antitubercular activity observed for some of these cinnamic derivatives, which may be amenable as future drugs for treating tuberculosis. This review intends to summarize the literature data on the antimicrobial activity of the natural cinnamic acids and related derivatives. In addition, selected hybrids between cinnamic acids and biologically active scaffolds with antimicrobial activity were also included. A comprehensive literature search was performed collating the minimum inhibitory concentration (MIC) of each cinnamic acid or derivative against the reported microorganisms. The MIC data allows the relative comparison between series of molecules and the derivation of structure-activity relationships.

Figure 1

Chemical structures of some therapeutically important cinnamic acid-containing molecules: ozagrel, cinromide and piplartine.

Figure 2

Chemical structures of trans- and cis-cinnamic acids

Figure 3

Chemical structures of differently substituted natural and synthetic cinnamic acids.

Figure 4

Chemical structures of cinnamic esters displaying antimicrobial activity.

Figure 5

Chemical structures of the cinnamic amides 78–131 with antimicrobial activity

Figure 6

Chemical structures of the cinnamic aldehydes, alcohols and related natural products.

Figure 7

Chemical structures of the cinnamic hybrids 152–184.