Synthesis, In-vitro antibacterial and antioxidant activity of chalcone derivatives

In the face of the emergence of bacteria resistant to common antibacterials and excessive accumulation of free radicals that can cause several diseases, it is important to look for new antibacterials and antioxidants. The goal of this work was to synthesize three chalcones derivatives by the Claisen-Schmidt condensation and then evaluate their antibacterial and antioxidant activities. The structure of these 3 compounds has been determined by NMR (¹H and ¹³C) spectroscopy. The in vitro antibacterial activity assessed by Microdilution methods, was tested against Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) and gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa) at different concentrations ranging from 7.82 to 1000 µg/mL. All three synthesized chalcones showed good antibacterial activity against gram positive and negative bacteria used with a range of MIC ranging from 62.50 to 1000 µg/mL. However, the (E)-3-(3, 4-dimethoxyphenyl)-1-(2-hydroxyphenyl) prop-2-en-1-one showed excellent activity against Bacillus subtilis with Minimum Inhibitory Concentration (MIC) of 62.5 µg/mL which is similar to that of the standard (Ampicillin) against the same bacterial strain. Antioxidant activity evaluated using 2,2-diphenyl2-picryl- hydrazyle ( DPPH) revealed that all the synthesized chalcones showed an antioxidant activity with IC₅₀ values of 8.22; 6.89 and 3.39 µg/mL for (E)-1-(2-hydroxyphenyl)-3-(4-hydroxyphenyl) prop-2-en-1-one, (E)-1-(2-hydroxyphenyl)-3-(4-methoxyphenyl) prop-2-en-1-one and (E)-3-(3, 4-dimethoxyphenyl)-1-(2-hydroxyphenyl) prop-2-en-1-one, respectively. These values are closer to that of ascorbic acid used as a standard. The results suggest that the synthesized chalcones, especially the (E)-3-(3, 4-dimethoxyphenyl)-1-(2-hydroxyphenyl) prop-2-en-1-one could be used, after in vivo and clinical tests, like antibacterial and antioxidant supplement or even replace current drug therapies.