Synthesis, Spectroscopic Characterization and Antibacterial Evaluation by Chalcones Derived of Acetophenone Isolated from Croton Anisodontus Müll.Arg.

Chalcones and their derivatives have been widely studied at research institutions and industries, in order to verify their biological properties against various diseases. In this work, it was carry out the synthesis of chalcones (E)-3-(furan-2-yl) -1- (2‑hydroxy-3,4,6-trimethoxyphenyl) prop‑2-en-1-one (HYTFURFURAL) and (E) -1- (2‑hydroxy-3,4-dimethoxyphenyl) -3-(thiophen-2-yl) prop‑2-en-1-one (HYTTHIOPHENE) by Claisen-Schmidt aldolic condensation reaction. The molecular structures of these new heteroaryl chalcones have been elucidated and characterized by 1H and 13C Nuclear Magnetic Resonance, Fourier transform Raman (FT-Raman), Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR), and Ultraviolet-Visible (UV–Vis) spectroscopy. Calculations using the Functional Density Theory (DFT) were performed to predict the vibrational wavenumbers and to obtain the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) molecular orbitals, and starting from them, the quantum descriptors: vertical ionization energy (I), vertical electron affinity (A), chemical potential (μ), electronegativity (χ), global hardness (η), and electrophilicity index (ω). Antimicrobial and modulatory antibiotic activities of these chalones were also investigated. The mechanism of the NorA and MepA efflux pump inhibition was also studied by means of molecular docking. The HYTFURFURAL and HYTTHIOPHENE chalcones did not present intrinsic activity against the tested bacterial strains; however, they were able to potentiate the activity of norfloxacin against the SA1199B (NorA) strain, as well as the activity of ciprofloxacin against the K2068 (MepA) strain. These results indicate that the HYTFURFURAL and HYTTHIOPHENE chalcones are promising compounds as adjuvants to the norfloxacin and ciprofloxacin antibiotics in the treatment of infections caused by S. aureus.