A series of thirty-two anilides of 3-(trifluoromethyl)cinnamic acid (series 1) and 4-(trifluoromethyl)cinnamic acid (series 2) was prepared by microwave-assisted synthesis. All the compounds were tested against reference strains Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 and resistant clinical isolates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant E. faecalis (VRE). All the compounds were evaluated in vitro against Mycobacterium smegmatis ATCC 700084 and M. marinum CAMP 5644. (2E)-3-[3-(Trifluoromethyl)phenyl]-N-[4-(trifluoromethyl)phenyl]prop-2-enamide (1j), (2E)-N-(3,5-dichlorophenyl)-3-[3-(trifluoromethyl)phenyl]prop-2-enamide (1o) and (2E)-N-[3-(trifluoromethyl)phenyl]-3-[4-(trifluoromethyl)-phenyl]prop-2-enamide (2i), (2E)-N-[3,5-bis(trifluoromethyl)phenyl]-3-[4-(trifluoromethyl)phenyl]-prop-2-enamide (2p) showed antistaphylococcal (MICs/MBCs 0.15–5.57 µM) as well as anti-enterococcal (MICs/MBCs 2.34–44.5 µM) activity. The growth of M. marinum was strongly inhibited by compounds 1j and 2p in a MIC range from 0.29 to 2.34 µM, while all the agents of series 1 showed activity against M. smegnatis (MICs ranged from 9.36 to 51.7 µM). The performed docking study demonstrated the ability of the compounds to bind to the active site of the mycobacterial enzyme InhA. The compounds had a significant effect on the inhibition of bacterial respiration, as demonstrated by the MTT assay. The compounds showed not only bacteriostatic activity but also bactericidal activity. Preliminary in vitro cytotoxicity screening was assessed using the human monocytic leukemia cell line THP-1 and, except for compound 2p, all effective agents did show insignificant cytotoxic effect. Compound 2p is an interesting anti-invasive agent with dual (cytotoxic and antibacterial) activity, while compounds 1j and 1o are the most interesting purely antibacterial compounds within the prepared molecules.

A series of eighteen 4-chlorocinnamanilides and eighteen 3,4-dichlorocinnamanilides were designed, prepared and characterized. All compounds were evaluated for their activity against gram-positive bacteria and against two mycobacterial strains. Viability on both cancer and primary mammalian cell lines was also assessed. The lipophilicity of the compounds was experimentally determined and correlated together with other physicochemical properties of the prepared derivatives with biological activity. 3,4-Dichlorocinnamanilides showed a broader spectrum of action and higher antibacterial efficacy than 4-chlorocinnamanilides; however, all compounds were more effective or comparable to clinically used drugs (ampicillin, isoniazid, rifampicin). Of the thirty-six compounds, six derivatives showed submicromolar activity against Staphylococcus aureus and clinical isolates of methicillin-resistant S. aureus (MRSA). (2E)-N-[3,5-bis(trifluoromethyl)phenyl]- 3-(4-chlorophenyl)prop-2-enamide was the most potent in series 1. (2E)-N-[3,5-bis(Trifluoromethyl)phenyl]-3-(3,4-dichlorophenyl)prop-2-enamide, (2E)-3-(3,4-dichlorophenyl)-N-[3-(trifluoromethyl)phenyl]prop-2-enamide, (2E)-3-(3,4-dichloro- phenyl)-N-[4-(trifluoromethyl)phenyl]prop-2-enamide and (2E)-3-(3,4-dichlorophenyl)- N-[4-(trifluoromethoxy)phenyl]prop-2-enamide were the most active in series 2 and in addition to activity against S. aureus and MRSA were highly active against Enterococcus faecalis and vancomycin-resistant E. faecalis isolates and against fast-growing Mycobacterium smegmatis and against slow-growing M. marinum, M. tuberculosis non-hazardous test models. In addition, the last three compounds of the above-mentioned showed insignificant cytotoxicity to primary porcine monocyte-derived macrophages.

Pattern 1-hydroxy-N-(2,4,5-trichlorophenyl)-2-naphthamide and the thirteen original carbamates derived from it were prepared and characterized. All the compounds were tested against Staphylococcus aureus ATCC 29213 as a reference and quality control strain and in addition against three clinical isolates of methicillin-resistant S. aureus (MRSA). Moreover, the compounds were evaluated against Enterococcus faecalis ATCC 29212, and preliminary in vitro cytotoxicity of the compounds was assessed using the human monocytic leukemia cell line (THP-1). The lipophilicity of the prepared compounds was experimentally determined and correlated with biological activity. While pattern anilide had no antibacterial activity, the prepared carbamates demonstrated high antistaphylococcal activity comparable to the used standards (ampicillin and ciprofloxacin), which unfortunately were ineffective against E. feacalis. 2-[(2,4,5-Trichlorophenyl)carba- moyl]naphthalen-1-yl ethylcarbamate (2) and 2-[(2,4,5-trichlorophenyl)carbamoyl]naphthalen-1-yl butylcarbamate (4) expressed the nanomolar minimum inhibitory concentrations (MICs 0.018–0.064 μM) against S. aureus and at least two other MRSA isolates. Microbicidal effects based on the minimum bactericidal concentrations (MBCs) against all the tested staphylococci were found for nine carbamates, while 2-[(2,4,5-trichlorophenyl)carbamoyl]naphthalen-1-yl heptylcarbamate (7) and 2-[(2,4,5-trichlorophenyl)carbamoyl]naphthalen-1-yl (4-phenylbutyl)carbamate (14) demonstrated MBCs in the range of 0.124–0.461 μM. The selectivity index (SI) for most investigated carbamates was >20 and for some derivatives even >100. The performed tests did not show an effect on the damage to the bacterial membrane, while the compounds were able to inhibit the respiratory chain of S. aureus.

Unsubstituted (2E)-N-phenyl-3-[2-(trifluoromethyl)phenyl]prop-2-enamide and six other ortho- or para-halogen-substituted anilides of 2-(trifluoromethyl)cinnamic acid were prepared. As the benzene nucleus of cinnamic acid itself is substituted in C₍₂₎ position with a trifluoromethyl moiety that is spatially close to both the amide bond and the halogen (F, Cl, CF₃) ortho-substitution of the anilide ring, interesting intramolecular interactions can be expected. Other derivatives are substituted at the para-position of the anilide ring, so that intermolecular interactions can be expected. Thus, it can be assumed that predicted properties, especially lipophilicity, will differ significantly from experimentally determined values. All the discussed compounds were analyzed using the reversed-phase high-performance liquid chromatography method. The procedure was performed under isocratic conditions with methanol as an organic modifier in the mobile phase using an end-capped non-polar C18 stationary reversed-phase column. In the present study, the structure–lipophilicity relationships of the studied compounds are discussed.

1-Hydroxy-N-phenylnaphthalene-2-carboxamide and a series of seventeen other carboxanilides in the anilide part of dichlorinated, trichlorinated, dibrominated, tribrominated, and chlorinated/brominated variants have recently been reported as biologically active compounds mainly with antibacterial, antimycobacterial, and anticancer effects. Since lipophilicity is one of the factors influencing the bioavailability (absorption, distribution, metabolism, and elimination), activity, and even toxicity of bioactive compounds, all the derivatives were investigated for their lipophilic and hydrophilic properties. All eighteen compounds were analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC). The procedure was performed under isocratic conditions with methanol as the organic modifier in the mobile phase using an end-capped non-polar C18 stationary reversed-phase column. The lipophilicity values are expressed as the logarithm of the capacity factor k (for the mobile phase water/methanol) and the distribution coefficients D at pH values of 6.5 and 7.4 (for the mobile phase buffer/methanol), as well as the calculated values of log P/Clog P by various methods. 1-Hydroxy-N-(3,4,5-trichlorophenyl)naphtha- lene-2-carboxamide and N-(4-bromo-3-chlorophenyl)-1-hydroxynaphthalene-2-carboxamide are the most lipophilic compounds of the whole series; on the other hand, surprisingly, unsubstituted 1-hydroxy-N-phenylnaphthalene-2-carboxamide is not the least lipophilic derivative. The mutual correlations between the experimental and predicted lipophilicity values are low; in addition, there are large deviations in the cross-correlations between log k and log D, which are due to the presence of a free ionizable phenolic group in the molecule.

Recently reported multihalogenated (CF₃/Cl) anilides of 1-hydroxynaphthalene-2-carboxanilides showed significant activity against both the reference strain Staphylococcus aureus ATCC 29213 and clinical isolates of methicillin-resistant S. aureus (MRSA). This fact inspired further investigation of the effect of these compounds on staphylococci. Chemoproteomics is a tool for investigating protein targets of potential drugs. It makes it possible to understand the effect of a bioactive molecule on a living system. An activity-based protein profiling (ABPP) method was employed using highly active and inactive ring-substituted 1-hydroxynaphthalene-2-carboxanilides as probes. The experiment was performed on the universally sensitive collection strain S. aureus ATCC 29213. Tryptic cleavage of proteins was performed prior to HPLC-MS/MS analysis. Protein profiles of control samples (S. aureus cells) and profiles of S. aureus treated with inactive/active derivatives were investigated and compared to one another. More than 1000 proteins were analyzed, with approximately 70% of the proteins increased and 30% of the proteins decreased after treatment with the investigated compounds. Treatment with the inactive compound mainly resulted in the expression of various proteins, so it can be assumed that the changes in the protein profile did not affect the basic biochemical pathways or that the microorganism was able to adapt by activating other pathways/expressing other proteins, surviving. Treatment with the highly active agent resulted in much smaller proteomic changes (mainly, the inhibition of several proteins compared to the inactive compound), and S. aureus failed to adapt and was killed.