Two-step synthesis of antibacterial Schiff base complexes
Researchers develop a 10-minute, two-step synthesis for amino acid Schiff base complexes using microwave irradiation and study their antibacterial properties.
Schiff bases were first discovered in the late 19th century and are organic compounds containing a carbon-nitrogen double bond (an imine bond). These molecules are used in a wide variety of applications including environmental sensors, catalysts, and in antibacterial, antifungal and anti-inflammatory drugs.
Metal derivatives of Schiff bases have antioxidant, antimicrobial and anticancer properties; copper complexes with amino acid groups show the most promising antimicrobial properties. “Amino acid Schiff base Cu(II) complexes have the potential to be used as antimicrobial agents but their wider applications are being limited by conventional methods for synthesis that often takes several hours and sometimes days. With our research, we aim to overcome this challenge by making the synthesis process more facile,” commented Takashiro Akitsu (Tokyo University of Science, Japan), who led a group of researchers from the Tokyo University of Science and the University of Technology of Compiègne (France).
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The research group succeeded in reducing the reaction time to just 10 minutes through a two-step synthesis using microwave irradiation and methanol as the solvent. This procedure could be used as a framework to synthesize other biologically active amino acid derivatives of Schiff base metal complexes in a more efficient way, which would make them more clinically desirable.
Methanol was chosen due to its high loss tangent, a measure of a solvent’s ability to convert microwave energy into heat at a given frequency and temperature. Microwave irradiation is often used in synthesis as it achieves controlled heating and accelerates reactions.
The researchers reported higher yields, improved purity and fewer by-products using this synthetic procedure compared to conventional methods, of which there are several.
The antimicrobial properties of these copper complex Schiff bases were assessed, comparing structures with no chlorine groups to those with one or two substituted chlorine groups. They found that complexes containing chlorine had better antibacterial properties than those without, with notable activity against E. coli. The chlorine-containing complexes also had antioxidant properties, meaning these compounds prevent or slow damage to cells caused by free radicals.
Next, the researchers are planning to analyze the toxicity of these compounds in kidney, liver and skin cells. Akitsu concluded: “Bacterial infectious diseases are a major threat to public health. Our study aims to contribute towards the improvement of health care systems in developing nations that are often affected by infectious epidemics.”
