In this work, we report the application of Buchwald-Hartwig amination for the preparation of new derivatives of quercetin and luteolin. Our investigation delves into the impact of aniline moiety on antioxidant, and anti-inflammatory activity, cytotoxicity, and the ability of flavonoids to modulate drug-resistance mechanisms in bacteria. The anti-inflammatory activity disappeared after the introduction of aniline into the flavonoids and the cytotoxicity remained low. Although the ability of quercetin and luteolin to modulate bacterial resistance to antibiotics has already been published, this is the first report on the molecular mechanism of this process. Both flavonoids attenuate erythromycin resistance by suppressing the ribosomal methyltransferase encoded by the ermA gene in Staphylococcus aureus. Notably, 4-(trifluoromethyl)anilino quercetin emerged as a potent ErmA inhibitor, likely by interacting with the RNA-binding pocket of ErmA. Additionally, both 4-fluoroanilino derivatives effectively impended the staphylococcal efflux system. All the prepared derivatives exhibited superior activity in modulating gentamicin resistance in S. aureus compared to the parent compounds. Overall, the incorporation of substituted anilines into the flavonoid core significantly enhanced its ability to combat multidrug resistance in bacteria.

Department of Biochemistry and Microbiology University of Chemistry and Technology Prague Technická 5 Prague 166 28 Czech Republic

Department of Clinical Microbiology and ATB Center Institute of Medical Biochemistry and Laboratory Diagnostics of the General University Hospital and of The 1st Faculty of Medicine of Charles University U Nemocnice 2 Prague 2 128 08 Czech Republic

Institute of Microbiology of the Czech Academy of Sciences Vídeňská 1083 Prague 142 00 Czech Republic

Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo nám 542 Prague 160 00 Czech Republic

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