Synthesis and biological evaluation of a new series of 4-alkoxy-2-arylquinoline derivatives as potential antituberculosis agents

Authors: GONCA TOSUN, TAYFUN ARSLAN, ZEYNEP İSKEFİYELİ, MURAT KÜÇÜK, ŞENGÜL ALPAY KARAOĞLU, NURETTİN YAYLI

Abstract: Three new series of 33 quinolone compounds, 2-(2-, 3-, and 4-fluorophenyl)-4-O-alkyl(C$_{5-15})$quinolines (7a-k, 8a-k, and 9a-k), were synthesized from 2-(2-, 3-, and 4-fluorophenyl)-2,3-dihydroquinolin-4(1H)-one (4, 5, and 6) by the reaction of alkyl halides under basic conditions in DMF. The new compounds 7a-k, 8a-k, and 9a-k were synthesized from flavonones 4-6, which can be considered new precursors for quinoline synthesis through a one-step reaction. All the target compounds (7a-k, 8a-k, and 9a-k) were evaluated for their in vitro antimicrobial activity against nine test microorganisms. They showed the most activity against Mycobacterium smegmatis with minimum inhibitory concentrations (MIC) of 62.5-500 $\mu $g/mL, indicating their potential uses as antituberculosis agents. Among them 8a-k (m-fluoride) were the most active compounds against M. smegmatis (MIC, 62.5-125 $\mu $g/mL). The newly synthesized title compounds were also evaluated for their in vitro antioxidant activities using DPPH• radical scavenging and FRAP tests. They showed at a low concentration (mg/mL) a range of SC$_{50}$ values of 0.03-12.48 mg/mL (DPPH•) and 0-722 $\mu $M (FRAP), respectively. The antioxidant results of compounds 7a-k, 8a-k, and 9a-k revealed that the length of the alkyl chain was negatively correlated with antioxidant capacity.

Keywords: Quinoline derivatives, flavonones, air oxidation, antimicrobial activity, antituberculosis activity, antioxidant activity

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