Influence of the Incubation Time on the Inhibition in the Aquatic Microcosm of Some Bacteria of Health Importance by Synthesized O-Propargyl vanillinic Chalcones
Background: The germs of waterborne diseases are often associated with an increase in resistance, which contrasts with the discovery of new active molecules, thus complicating treatment. Research is therefore undertaken to discover new substances with therapeutic potential. Although plants are an important source for obtaining interesting compounds, methods based on synthetic chemistry make it possible to obtain compounds inspired by those found in nature and presenting equally important properties. One group of these compounds, called chalcone, is of great importance nowadays due to the diversity of biological activities it presents; therefore, many chalcone derivatives are synthesized and their biological activities evaluated. Methodology: The compounds were synthesized by Claisen-Schmidt condensation in a basic medium (potash 5%). The reaction was followed by thin layer chromatography. At the end of the reaction, filtration after cooling of the reaction medium allowed the collection of part of the product that precipitated, while liquid-liquid extraction (water-acetate) allowed to obtain the rest still dissolved. The products obtained were purified by column chromatography using the Hexane/Ethyl Acetate system. The characterization of the products was carried out on the physical properties and also the nuclear magnetic resonances of the proton and carbon 13. The use of isolation media for each of the 04 bacteria studied, namely ENDO, SS, TCBS and BEA agars, permitted the isolation of Escherichia coli, Salmonella typhi, Vibrio cholerae and Streptococcus feacalis, respectively. The microbiological technique for counting bacterial colonies in solid medium, as well as the microdilution in liquid medium allowed the evaluation of the action of the different chalcones. Results: Four O-propargyl vanillinic chalcones 5a-5d were obtained by Claisen Schmidt condensation method with respective yields of 63.6%; 66.7%; 66.7% and 70.0%. The evaluation of their antibacterial activities was done on four strains of bacteria including E. coli, S. typhi, V. cholerae and S. feacalis isolated from wells in the city of Yaoundé. Statistical data from the results of the solid-state bacterial colony counting technique revealed a lack of significance (p > 0.05) with respect to the variation of the mean bacterial abundance as a function of the concentrations of each chalcone (except that of the S. feacalis with respect to compound 5b). The results of the microdilution test showed the lowest MIC values with compound 5d (250 µg/mL), against S. typhi. Chalcones 5c and 5d exhibited better activity on E. coli (MIC value of 500 µg/mL) compared to the reference antibiotic: ampicillin (MIC > 1000 µg/mL). Chalcones 5a and 5b were the least active on all bacteria studied, with MIC values greater than or equal to 1000. Conclusions: The microdilution tests showed an antibacterial activity of the synthesized compounds, with a better activity for the chalcone 5d.