Antimicrobial, Antioxidant, and Anti-inflammatory Evaluation of Synthesised Azo Compounds based on β-naphthol, Catechol and Quinol Nucleus

Abstract

A series of 10-aryl substituted azo dyes were synthesized by coupling of β-naphthol, catechol, and quinol with different aromatic amines. The synthetic compounds were screened for their in vitro antimicrobial, antioxidant, and anti-inflammatory activities. The characterization of the synthesized compounds was carried out by UV, IR, 1H NMR and Mass spectroscopy. 13C NMR was employed to confirm the structural identity of some of the compounds.  After screening for the presence of antimicrobial constituents in the azo compounds using HTSPOTi culture method, quinol compounds 7 [(E)-2(2nitrophenyl) diazenyl) benzene-1,4-diol] and 10 [(E)-2-(3-nitrophenyl) diazinyl) benzene-1,4-diol] were the most active in terms of broad spectrum activity against  Gram-positives [Staphylococcus aureus (ATCC 25923), Streptococcus pyrogenes (clinical strain), Enterococcus faecalis (ATCC 29212)],, Gram-negatives [Salmonella typhi (clinical strain), Escherichia coli (ATCC 251922)] and Pseudomonas aeruginosa (ATCC 27853)  and the Candida albicans at minimum inhibitory concentrations of 15.63-31.25 µg/mL. A quinol derivative, [(E)-2-(2nitrophenyl) diazinyl) benzene-1, 4-diol], exhibited the best anti-inflammatory activity in the heat-denatured egg albumin assay. Compounds [ethyl (Z)-4-(3-hydroxynapthalen-1-yl (diazinyl) benzoate] and (E)-2-((3-nitrophenyl) diazenyl) benzene-1,4-diol showed high DPPH free radical scavenging activity during the antioxidant assay.