Multipurpose azo pyridone dyes: synthesis, characterization, antioxidant and antimicrobial activity

Abstract

Wide commercial application of azo pyridone dyes rests on the cost-effectiveness of their preparation and almost innumerable possibilities for the synthesis by combining various diazo and coupling pyridone components that enable tuning of targeted properties. The great significance of these dyes in the last few decades is due to their outstanding properties, such as vivid colors and good color fastness properties. Azo pyridone dyes are also applicable in different coloration related processes such as inkjet printing and liquid crystal displays. On the other hand, they are recognized as valuable compounds in biological studies, as they possess antioxidant, antimicrobial and antiproliferative properties. In this work, three novel 6-hydroxy-4-methyl-1-pyridinium-2-pyridone based dyes bearing three bioactive heterocyclic rings in their structures are synthesized, wherein thiazole based anilines (2-aminothiazole, 2-aminobenzothiazole, 6-methoxy-2-aminobenzothiazole) are used as diazo components. The compounds are characterized by melting points, NMR and FTIR spectroscopy. The solvatochromic properties are investigated in solvents of different properties. Furthermore, the antioxidant capacities of the compounds are evaluated by ABTS (2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) assay, while antimicrobial activity is determined by broth microdilution method against five bacterial strains (S. aureus, E. faecalis, B. subtilis, E. coli and K. pneumoniae) and one fungal strain (C. albicans).

Široka komercijalna upotreba piridonskih azo boja zasniva se na njihovoj relativno jeftinoj i jednostavnoj pripremi, kao i činjenici da se veliki broj kuplujućih i diazo komponenti mogu međusobno kombinovati kako bi se dobile boje odgovarajućih svojstava. Veliki značaj ovih boja poslednjih nekoliko decenija, ogleda se u njihovim istaknutim svojstvima kao što su živopisna obojenja i dobra postojanost. Ove boje, takođe, nalaze primenu u ink-džet štampi i LCD ekranima. Sa druge strane, ove boje predstavljaju značajna jedinjenja u biološkim studijama, jer poseduju antioksidativnu, antimikrobnu i antiproliferativnu aktivnost. U ovom radu, sintetisane su tri boje koje u svojoj strukturi obuhvataju tri bioakativna heterociklična jezgra, pri čemu je kao kuplujuća komponenta korišćen 6-hidroksi-4-metil-1-piridinijum-2-piridon, a kao diazo komponente anilini na bazi tiazola (2-aminotiazol, 2-aminobenzotiazol i 6-metoksi-2-aminobenzotiazol). Jedinjenja su okarakterisana temperaturom topljenja, NMR i FTIR spektroskopijama. Solvatohromna svojstva su ispitana u rastvaračima različitih svojstava. Antioksidativna aktivnost jedinjenja ispitana je ABTS (2,2'-azino-bis-3-etilbenzotiazolin-6-sulfonat) testom, dok je minimalna inhibitorna koncentracija ispitana primenom mikrodilucione metode u bujonu prema 5 bakterijskih sojeva (S. aureus, E. faecalis, B. subtilis, E. coli i K. pneumoniae), kao i prema oportunističkoj gljivici C. albicans.