This post was written by Nathan Schneider. His article was entitled ” Synthesis and Antibacterial Activity of Some New Derivatives of Pyrazole.”
Introduction:
The synthesis of bioactive compounds is an area of study of great interest to the medical field, especially compounds with antimicrobial effects. Through synthesizing new compounds and studying their properties and bioactivity, scientists can discover new and possibly more effective antibiotics. Derivatives of the molecule pyrazole have been used for their effects as an anti-inflammatory, antipyretic, anticonvulsant, anti-arrhythmic, and antibacterial agent. In recent years, some new derivatives of Pyrazole have been synthesized and evaluated for their antimicrobial activity. In the study Synthesis and antibacterial activity of some new derivatives of pyrazole conducted by Mohammad Rahimizadeh, Mehdi Pordel, Mehdi Bakavoli, Shima Rexaeian, and Ali Sadeghian, some new derivatives of pyrazole were assessed for their antibacterial effects with gram-positive bacteria. In this study, certain derivatives of pyrazole were analyzed and observed to “show moderate to strong antimicrobial activities against gram positive bacteria”. 1
Methods:
In this experiment, 10 different derivatives of pyrazole were obtained by synthesizing different acid chlorides with the compound “5-amino-1-(2,4-dinitrophenyl)-H-4-pyrazolecarbonitrile” (1). The 5-amino-1-(2,4-dinitrophenyl)-H-4-pyrazolecarbonitrile was obtained from the reaction of 1-(2,4-dinitrophenyl)hydrazine with 2-(ethoxymethylene) malononitrile in ethanol under reflux condition. The acid chlorides that were used in the reaction with the 5-amino-1-(2,4-dinitrophenyl)-H-4-pyrazolecarbonitrile were either purchased, or obtained through the reaction of thionyl chloride and a carboxylic acid. The final step in obtaining the pyrazole derivatives was the synthesis of the acid chlorides with the 5-amino-1-(2,4-dinitrophenyl)-H-4-pyrazolecarbonitrile in dry pyridine for a four-hour reflux.
Results:
The resulting pyrazole derivatives were analyzed for melting point, absorption of the IR spectra, elemental percentage, and percent yield. They were further tested for antibacterial activity against Escherichia coli, Staphylococcus areus, methicillin susceptible S. aureus, Pseudomonas aeruginosa, and Bacillus subitilis. Against all of the gram-negative bacteria, the pyrazole derivatives were uninhibitory, but against Staphylococcus areus and methicillin susceptible S. aureus, different derivatives showed “moderate to strong antimicrobial activity.” 1 The study did comparative measurements against Erythromycin, Cloxacillin, and Cephalexin and two of the derivatives had lower minimum inhibitory concentrations than that of Erythromycin, Cloxacillin, and Cephalexin against either Staphylococcus areus, or methicillin susceptible S. aureus (these derivatives had substituted R groups of para-nitrobenzene and para-cyanobenzene). Minimum inhibitory concentrations were obtained through use of dilution test tub method, and then confirmed by culturing samples of bacteria on Petri dishes and determining the minimum inhibitory concentration of the test organism by detecting a lack of visual turbidity.
Conclusions and Discussion:
The results of this experiment demonstrate how certain new derivatives of pyrazole have a strong antibacterial capability against certain forms of gram-positive bacteria. This capability was demonstrated to be stronger than some antibiotics being used at the time of the study. The procedures of the experiment appear to be sound in aspects of both chemistry and biology. The chemical procedures, equipment, and sources of materials are all documented, and the antibacterial capabilities of the pyrazole derivatives were tested with both test tube dilution method, and in Petri dishes for the elimination of visual turbidity. Moreover, they were tested against Erythromycin, Cloxacillin, and Cephalexin, all current antibiotics on the market during the time of study. Overall, the study appears to be well put together, conducted, and documented.
After this study it would be unlikely that someone would argue against the antibacterial capabilities of the assessed pyrazole derivatives, and from this study, further experiments can be conducted using these derivatives to assess their safety and effectiveness for consumption. While we currently do not know if these derivatives will ever be used for drug design or antimicrobial therapeutics, this study can now be used as a foundation for the further experimentation and examination of these pyrazole derivatives because it was conducted accurately and effectively.
