Abstract

The antimicrobial screening of the monoazo dyes, 4-carboxyl-2, 6-dintropheylazohydroxynapththalene, was carried out as a preliminary test for evaluating their biological potentials. Antimicrobial screening was done with filter paper disc and gauze bandage fabric impregnated with the dyes using 7 microbial isolates: Staphylococcus aureus 382, Candida albicans UBA7, Klebsiella species 864, Escherichia coli V₃, Salmonella enterica gallinarum 28 V₂, Pseudomonas aeruginosa and Proteus species. Diameters of zones of inhibitions were measured to evaluate the activities of the dyes. The minimum inhibitory concentration of the four title dyes was thereafter estimated using two sensitive strains of S. aureus andCandida albicans. AZ-01 and AZ-04 at a concentration of 5 mg/mL was found to have the highest activities of 20 mm each on S. aureus, comparable to the positive control gentamicin (diameter of 20 mm), using paper disc. With the fabric screening using 5 mg/mL and 10 mg/mL concentration, only the 5 mg/mL AZ-01 and the 10 mg/mL AZ-01 had activities of 10 and 12 mm respectively on S. aureus. On C. albicans, 5 mg/mL AZ-01 and 10 mg/mL AZ-01 had activities of 20 and 24 mm respectively and these were found comparable to the positive control 1% tioconazole. 5 mg/mL AZ-02 and 10 mg/mL AZ-02 had activities of 10 and 14 mm respectively, 5 mg/mL AZ-04 and 10 mg/mL AZ-04 had activities of 16 and 16 mm, respectively. The minimum inhibitory concentration (MIC) done using serial dilution on WHO microtitre plate (96 wells), gave AZ-01 having the highest activity, both on S. aureus and C. albicans with MIC of 15.63 µg/mL, and then AZ-04 with MIC of 23.44 µg/mL. The results of these microbial assays suggest that the investigated monoazo dyes may be useful as potential antimicrobial agents, especially against multidrug resistant S. aureus, in addition to their dyeing properties.

Key words: 4-carboxyl-2, 6-dinitrophenylazohydroxynaphthalenes, antimicrobial properties, multidrug resistant Staphylococcus aureus, MIC.