Nurul Asma Razali, Zuhair Jamain, Fauze Mahmud, Dayang Najwa Datu Borhan
Azo compounds, known for their durability and chemical stability, are being studied for their antifungal potential. This study aims to synthesize and evaluate a new series of azo-based compounds with varying terminal groups to assess their bioactivity. Compounds 4(a-d), containing a nitro group, and compound 5(a-d), containing a hydroxy group, were synthesized via a multistep reaction sequence, with percentage yields ranging between 79.5 and 98.6%. Structural characterization of representative compounds 4a and 5a were confirmed by FTIR, NMR and CHN analyses. Compound 4a, displayed several characteristics band in the FTIR spectrum [1538 cm-1 (N=N) and 1496 & 1348 cm-1 (NO)], while compound 5a, [1516 cm-1 (N=N) and 3390 cm-1 (OH)]. In the 1H NMR spectra, 4a showed resonances corresponding to amide (δ 9.82 ppm), while 5a displayed signals for amide (δ 10.28 ppm) and hydroxyl (δ 9.68 ppm). In the 13C NMR spectra, the main differences are attributable to the substituents: compound 4a had aromatic carbons shifted downfield near the nitro group, while compound 5a had a hydroxyl-substituted aromatic carbon. CHN elemental confirmed the purity of both compounds 4a and 5a, with minimal deviation from theoretical values of 0.14 and 0.13%, respectively. Derivatives 4a (LC50: 315.6 ppm) and 5a (LC50: 230.0 ppm) were selected for further antifungal evaluation after preliminary cytotoxicity screening. Antifungal screening used disk diffusion and microdilution methods to assess potency. Compound 4a showed better antifungal activity against Candida albicans, with an inhibition zone of 12 mm (1.0 M) and 12 mm (0.5 M), respectively, whereas compound 5a produces 12 mm and 10 mm at the same concentrations. The MIC testing showed that compound 4a achieved complete inhibition at 0.625 mM, with an IC50 value of 0.2816 mM, while compound 5a did not reach complete inhibition and displayed a higher IC50 value of 0.8110 mM.