Synthesis, antimicrobial activity of Schiff base compounds of cinnamaldehyde and amino acids

Microorganism infection is a continue threat to human health. About the control the infection, using antimicrobial agent is one of the effective options. Now, natural antimicrobial agents are focused extensively because they are low-toxic and safe. Cinnamaldehyde is a natural antimicrobial substance, which is extracted from bark of  Cinnamomum genus trees. Cinnamaldehyde possesses good bioactivity and could inhibit the growing of many kinds of fungi and bacteria. Cinnamaldehyde is categorized as Generally Recognized as Safe (GRAS) by the U.S. Food and Drug Administration. However, Cinnamaldehyde has several drawbacks, such as its strong odor, high volatility and water insolubility, which limited its application.

In our research, cinnamaldehyde was modified by amino acids to synthesize a new class of Schiff base compounds. Bioactivity results indicated that the Schiff base compounds remarkably inhibited the growth of the tested bacteria and fungi, and they have broad-spectrum antimicrobial activity. Compared with control compounds, i.e. Ciprofloxacin and Fluconazole, most of the Schiff base compounds exhibited better bioactivity than the two control compounds.

The key finding of this study is that, the new class of cinnamaldehyde Schiff base compounds, which could be easily synthesized, have great bioactivity, low-toxicity, low odor and good water solubility. Therefore, cinnamaldehyde Schiff base compounds were potential to be antibacterial agents or food preservatives.

Moreover, the further analysis on antimicrobial activity and chemical structure were conducted in our research. Results from the structure-activity relationship suggest that both p-Cl of benzene ring from cinnamaldehyde and the number of –COOK from amino acid salts significantly contributed to their antimicrobial activity.

Our research results provided an alternative option for exploring of new antimicrobial agents.