Synthesis and Antimicrobial Profiling of a Pyrazole-Based Schiff Base Incorporating 2,4-Dihydroxybenzaldehyde

Abstract

In this study, a Schiff base (DHB-Pz) was synthesized via a condensation reaction between 5-amino-3-methyl-1-phenylpyrazole and 2,4-dihydroxybenzaldehyde. The compound was characterized using elemental analysis, FTIR, UV-Vis spectroscopy, and conductivity measurements. The FTIR spectrum confirmed the formation of the azomethine linkage (C=N) through a distinct stretching band, while UV-Vis absorption at 412 nm indicated extended conjugation. The Schiff base was screened for antimicrobial activity against a panel of Gram-positive (Bacillus subtilis, Serratia sp.) and Gram-negative (Klebsiella sp., Proteus sp.) bacteria, as well as fungi (Candida albicans and Aspergillus niger) using the agar well diffusion method. Minimum inhibitory concentrations (MICs) were determined using serial dilution techniques. The compound exhibited broad-spectrum antimicrobial activity with MIC values as low as 0.312 mg/mL for Aspergillus niger, and comparable potency to reference drugs (Gentamycin and Nystatin). The promising activity may be attributed to the presence of hydroxyl groups, the pyrazole moiety, and the conjugated system, which enhance membrane interaction and disruption. These findings underscore the potential of DHB-Pz as a scaffold for future antimicrobial agent development.