African Journal of Microbiology Research Vol. 4(22) pp. 2444-2450, 18 November, 2010 Available online http://www.academicjournals.org/ajmr ISSN 1996-0808 ©2010 Academic Journals Full Length Research Paper Antimicrobial properties of 4-Carboxyl-2, 6- dinitrophenylazohydroxynaphthalenes Olajire A. Adegoke 1 *, Akinlabi O. Ogunleye 2 , Oluwafunmilayo T. Lawal 3 , Olakunle S. Idowu 1 and Mukaram A. Adeniyi-Akee 1 1 Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Ibadan, Ibadan, Nigeria. 2 Faculty of Veterinary Medicine, Department of Veterinary Microbiology and Parasitology, University of Ibadan, Ibadan, Nigeria. 3 Department of Pharmaceutical Microbiology, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria. Accepted 28 October, 2010 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 V 3 , Salmonella enterica gallinarum 28 V 2 , 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 and Candida 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. INTRODUCTION Antimicrobial properties of incorporated dyes in food, beverages, cosmetics and fabrics become desirable as that prolong the utility of such products by inhibiting bacterial and fungal growth. Dixit B.C. Patel and Desai, 2007 worked on the antimicrobial and fabric-protective *Corresponding author. E-mail: jireade@yahoo.com. Tel: +234 803 638 1625. activities of naphthol- based azo dyes using 2,4- dihydroxybenzophenone, an aromatic ketone (diphenyl ketone), as an important starting material in organic synthesis of dyes. They showed that the antimicrobial properties of these azo dyes reduced and prevent damages made to the mechanical strength of materials, colour changes, stains and stale odour. Azo dyes produced from naphthols and phenol has wide applications as polymer additives (Yurteri et al., 2002). Their hydroxyl groups are good UV light absorbers which