Synthesis, Characterization and Antimicrobial Studies of Four Chalcone Derivatives

The increasing prevalence of antimicrobial resistance has intensified the search for structurally simple and biologically active compounds with therapeutic potential. In this study, four chalcone derivatives (A, B, C and D) were synthesized via Claisen–Schmidt condensation using substituted aromatic aldehydes and acetophenone under mild alkaline conditions. The synthesized compounds were obtained in good yields (73–81.9%), with masses ranging from 0.58–0.65 g and melting point ranges of 71–206°C. The compounds were purified and confirmed by thin-layer chromatography and melting point determination, while structural elucidation was achieved using Fourier Transform Infrared (FT-IR) spectroscopy, with spectra recorded over the range of 650–4000 cm⁻¹, and Gas Chromatography–Mass Spectrometry (GC–MS), which confirmed molecular ions at m/z 223.0, 242.2, 222.0 and 251.0 for compounds A, B, C and D, respectively. The compounds were evaluated for antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Salmonella typhimurium, and antifungal activity against Candida albicans using the agar well diffusion method. All derivatives exhibited antimicrobial activity, producing inhibition zones ranging from 12–22 mm, with minimum inhibitory concentrations (MICs) of 3.13–50 mg/mL. Compound A (4-amino-substituted chalcone) demonstrated the highest antimicrobial potency, exhibiting the largest zones of inhibition (up to 22 mm against Escherichia coli), the lowest MIC values (3.13–12.5 mg/mL), and bactericidal activity at 25–50 mg/mL. The enhanced activity is attributed to the electron-donating amino substituent, which likely improves interactions with microbial targets.