Síntese, caracterização e avaliação da atividade antimicrobiana de diazenil chalconas

Abstract

Chalcones are aromatic ,-unsaturated ketones that constitute a class of flavonoids reported in the literature for their wide variety of biological activities, such as anti-inflammatory, antibacterial, antileukemic, antimalarial and antioxidant. In the search for new compounds with antimicrobial activity, this work aimed to synthesize diazenyl chalcones starting from 3- and 4-aminoacetophenone, using two strategies. Firstly, 4-aminoacetophenone was converted into diazenyl acetophenone by the diazotation reaction and coupling with cyclic amines (pyrrolidine, piperidine and morpholine), to form chalcones by the Claisen-Schmidt condensation reaction. In the second methodology, first the aminoacetophenone was converted into the chalcone, by the condensation reaction, and then diazotation and coupling with the amines were carried out. All compounds obtained were purified and characterized by spectroscopy in the mid-infrared region and melting points. Yield rates and melting points were obtained with values ranging from 50 - 84% and 72 - 260 °C. The chalcones were evaluated for their antimicrobial potential by broth microdilution and subculture methods to determine the inhibitory, bactericidal and minimum fungicide concentration (MIC, MBC and MFC). The diazenyl chalcone substituted with the –OH and piperidine group in positions 6 and 5 of the aromatic rings, respectively (C1), presented the highest MIC and MFC values against the strain of the fungus Candida albicans with values of 1000 and 500 μg/mL respectively. The compounds substituted with the groups nitro and piperidine (B1), nitro and morpholine (B2), nitro and pyrrolidine (B3), in positions 4 and 4' of the aromatic rings, and hydroxyl and piperidine (C1) showed inhibition of bacterial growth against the bacteria E. coli, but they did not present bactericidal potential. None of the compounds tested showed activity against the bacteria Staphylococcus aureus and Pseudomonas aeruginosa. All the compounds synthesized in this work are unpublished, with the exception of compound A2, diazenyl acetophenone with morpholine substitution in the para position of the aromatic ring.