BACKGROUND AND PURPOSE: New compounds and innovative therapeutic approaches are trying to prevent antimicrobial resistance, which has become a global health challenge. EXPERIMENTAL APPROACH: This study includes a series of twelve mono-, di- and trichlorinated 1-hydroxynaphthalene-2-carboxanilides designed as multitarget agents. All compounds were evaluated for their antistaphylococcal activity. Furthermore, MTT assay and chemoproteomic analysis of selected compounds were performed. Cytotoxicity in human cells was also tested. KEY RESULTS: N-(3,5-Dichlorophenyl)-1-hydroxynaphthalene-2-carboxamide (10) demonstrated activity comparable to or higher than clinically used drugs, with minimum inhibitory concentrations (MICs) of 0.37 μM. The compound was equally effective against clinical isolates of methicillin-resistant S. aureus. On the other hand, compound 10 showed 96 % inhibition of S. aureus respiration only at a concentration of 16× MIC. Chemoproteomic analysis revealed that the effect of agent 10 on staphylococci resulted in the downregulation of four proteins. This compound expressed no in vitro cytotoxicity up to a concentration of 30 μM. CONCLUSION: From the set of tested mono-, di- and trisubstituted derivatives, it is evident that the position of chlorine atoms is decisive for significant antistaphylococcal activity. Inhibition of energy metabolism does not appear to be one of the main mechanisms of action of compound 10; on the contrary, the antibacterial effect may likely be contributed by downregulation of proteins (especially ATP-dependent protease ATPase subunit HslU) involved in processes essential for bacterial survival and growth, such as protein, nucleotide/nucleic acid synthesis and efficient protein repair/degradation.

• Keywords
• Lipophilicity, MTT assay, antistaphylococcal activity, chemoproteomic analysis, cytotoxicity,
• Publication type
• Journal Article MeSH

BACKGROUND AND PURPOSE: Many new compounds are being prepared to overcome the problem of increasing microbial resistance and the increasing number of infections. EXPERIMENTAL APPROACH: This study includes a series of twenty-seven mono-, di- and trisubstituted 2-hydroxynaphthalene-1-carboxanilides designed as multitarget agents. The compounds are substituted with methoxy, methyl, and nitro groups, as well as additionally with chlorine, bromine, and trifluoromethyl at various positions. All the compounds were evaluated for antibacterial activities against Gram-positive and Gram-negative bacteria and mycobacteria. Cytotoxicity on human cells was also tested. KEY RESULTS: Three compounds showed activity comparable to clinically used drugs. N-(3,5-Dimethylphenyl)-2-hydroxynaphthalene-1-carboxamide (13) showed only antistaphylococcal activity (minimum inhibitory concentration (MIC) = 54.9 μM); 2-hydroxy-N-[2-methyl-5-(trifluoromethyl)phenyl]naphthalene-1-carboxamide (22) and 2-hydroxy-N-[4-nitro-3-(trifluoromethyl)phenyl]naphthalene-1-carboxamide (27) were active across the entire spectrum of tested bacteria/mycobacteria, both against the sensitive set and against resistant isolates (MICs range 0.3 to 92.6 μM). Compound 22 was even active against E. coli (MIC = 23.2 μM). The active agents showed no in vitro cytotoxicity up to a concentration of 30 μM. CONCLUSION: Compounds with trifluoromethyl in the meta-anilide position, experimental lipophilicity expressed as log k (logarithm of the capacity factor) in the range of 0.31 to 0.34 and calculated electron σ parameter for the anilide substituent higher than 0.59 were effective. The investigated compounds meet the definition of Michael acceptors. Based on ADME screening, the investigated compounds 13, 22 and 27 should have suitable physicochemical parameters for good bioavailability in the organism. Therefore, these are promising agents for further study.

• Keywords
• Lipophilicity, antibacterial activity, antimycobacterial activity, cytotoxicity,
• Publication type
• Journal Article MeSH

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.

• Keywords
• Michael acceptors, antimicrobial activity, cinnamamides, cytotoxicity, docking study, lipophilicity, structure–activity relationships,
• MeSH
• Anti-Bacterial Agents pharmacology   chemistry   MeSH
• Cinnamates pharmacology   chemistry   MeSH
• Humans MeSH
• Methicillin-Resistant Staphylococcus aureus * MeSH
• Microbial Sensitivity Tests MeSH
• Staphylococcal Infections * MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Cinnamates MeSH
• cinnamic acid MeSH Browser

A new method for modifying the structure of tetracyclic quinobenzothiazinium derivatives has been developed, allowing introduction of various substituents at different positions of the benzene ring. The method consists of reacting appropriate aniline derivatives with 5,12-(dimethyl)thioquinantrenediinium bis-chloride. A series of new quinobenzothiazine derivatives was obtained with propyl, allyl, propargyl and benzyl substituents in 9, 10 and 11 positions, respectively. The structure of the obtained compounds was analyzed by 1H and 13C NMR (HSQC, HMBC) and X-ray analysis. All the compounds were tested against reference strains Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212, and representatives of multidrug-resistant clinical isolates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant E. faecalis (VRE). In addition, all the compounds were evaluated in vitro against Mycobacterium smegmatis ATCC 700084 and M. marinum CAMP 5644. 9-Benzyloxy-5-methyl-12H-quino [3,4-b][1,4]benzothiazinium chloride (6j), 9-propoxy-5-methyl-12H-quino[3,4-b][1,4]benzothiazinium chloride (6a) and 9-allyloxy-5-methyl-12H-quino[3,4-b][1,4]benzothiazinium chloride (6d) demonstrated high activity against the entire tested microbial spectrum. The activities of the compounds were comparable with oxacillin, tetracycline and ciprofloxacinagainst staphylococcal strains and with rifampicin against both mycobacterial strains. Compound 6j 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 of the compounds performed using normal human dermal fibroblasts (NHDF) proved that the tested compounds showed an insignificant cytotoxic effect on human cells (IC50 > 37 µM), making these compounds interesting for further investigation. Moreover, the intermolecular similarity of novel compounds was analyzed in the multidimensional space (mDS) of the structure/property-related in silico descriptors by means of principal component analysis (PCA) and hierarchical clustering analysis (HCA), respectively. The distance-oriented structure/property distribution was related with the experimental lipophilic data.

• Keywords
• antibacterial activity, azaphenothiazines, cytotoxicity, descriptor-based similarity analysis, phenothiazine,
• MeSH
• Anti-Bacterial Agents chemistry   MeSH
• Chlorides pharmacology   MeSH
• Humans MeSH
• Methicillin-Resistant Staphylococcus aureus * MeSH
• Microbial Sensitivity Tests MeSH
• Mycobacterium * MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Chlorides MeSH

A series of eleven benzylated intermediates and eleven target compounds derived from salicylanilide were tested against Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 as reference strains and against three clinical isolates of methicillin-resistant S. aureus (MRSA) and three isolates of vancomycin-resistant E. faecalis. In addition, the compounds were evaluated against Mycobacterium tuberculosis H37Ra and M. smegmatis ATCC 700084. The 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. The benzylated intermediates were found to be completely biologically inactive. Of the final eleven compounds, according to the number of amide groups in the molecule, eight are diamides, and three are triamides that were inactive. 5-Chloro-2-hydroxy-N-[(2S)- 4-(methylsulfanyl)-1-oxo-1-{[4-(trifluoromethyl)phenyl]amino}butan-2-yl]benzamide (3e) and 5-chloro-2-hydroxy-N-[(2S)-(4-methyl-1-oxo-1-{[4-(trifluoromethyl)phenyl]amino)pentan-2-yl)benzamide (3f) showed the broadest spectrum of activity against all tested species/isolates comparable to the used standards (ampicillin and isoniazid). Six diamides showed high antistaphylococcal activity with MICs ranging from 0.070 to 8.95 μM. Three diamides showed anti-enterococcal activity with MICs ranging from 4.66 to 35.8 μM, and the activities of 3f and 3e against M. tuberculosis and M. smegmatis were MICs of 18.7 and 35.8 μM, respectively. All the active compounds were microbicidal. It was observed that the connecting linker between the chlorsalicylic and 4-CF3-anilide cores must be substituted with a bulky and/or lipophilic chain such as isopropyl, isobutyl, or thiabutyl chain. Anticancer activity on THP-1 cells IC50 ranged from 1.4 to >10 µM and increased with increasing lipophilicity.

• Keywords
• antimicrobial activity, cytotoxicity, lipophilicity, peptidomimetics, salicylamide, structure–activity relationships,
• MeSH
• Ampicillin MeSH
• Anilides MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Benzamides MeSH
• Isoniazid MeSH
• Humans MeSH
• Methicillin-Resistant Staphylococcus aureus * MeSH
• Microbial Sensitivity Tests MeSH
• Mycobacterium tuberculosis * MeSH
• Peptidomimetics * MeSH
• Salicylanilides pharmacology   MeSH
• Vancomycin MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Ampicillin MeSH
• Anilides MeSH
• Anti-Bacterial Agents MeSH
• Benzamides MeSH
• Isoniazid MeSH
• Peptidomimetics * MeSH
• salicylanilide MeSH Browser
• Salicylanilides MeSH
• Vancomycin MeSH

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.

• Keywords
• antistaphylococcal activity, carbamates, cytotoxicity, hydroxynaphthalenes, lipophilicity, structure–activity relationships,
• Publication type
• Journal Article MeSH

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.

• Keywords
• antimicrobial activity, cinnamamides, cytotoxicity, lipophilicity, structure-activity relationships,
• MeSH
• Ampicillin pharmacology   MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Methicillin-Resistant Staphylococcus aureus * MeSH
• Microbial Sensitivity Tests MeSH
• Mycobacterium tuberculosis * MeSH
• Swine MeSH
• Mammals MeSH
• Staphylococcal Infections * MeSH
• Staphylococcus aureus MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Ampicillin MeSH
• Anti-Bacterial Agents MeSH

A set of twenty-four 3-hydroxynaphthalene-2-carboxanilides, disubstituted on the anilide ring by combinations of methoxy/methyl/fluoro/chloro/bromo and ditrifluoromethyl groups at different positions, was prepared. The compounds were tested for their ability to inhibit photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. N-(3,5-Difluorophenyl)-, N-(3,5-dimethylphenyl)-, N-(2,5-difluorophenyl)- and N-(2,5-dimethylphenyl)-3-hydroxynaphthalene-2-carboxamides showed the highest PET-inhibiting activity (IC50 ~ 10 µM) within the series. These compounds were able to inhibit PET in photosystem II. It has been found that PET-inhibiting activity strongly depends on the position of the individual substituents on the anilide ring and on the lipophilicity of the compounds. The electron-withdrawing properties of the substituents contribute towards the PET activity of these compounds.

• Keywords
• PET inhibition, hydroxynaphthalene-carboxamides, spinach chloroplasts, structure-activity relationships,
• MeSH
• Chloroplasts drug effects   metabolism   MeSH
• Photosynthesis drug effects   MeSH
• Photosystem II Protein Complex antagonists & inhibitors   metabolism   MeSH
• Herbicides chemistry   metabolism   MeSH
• Naphthalenes chemistry   metabolism   MeSH
• Spinacia oleracea drug effects   metabolism   MeSH
• Electron Transport drug effects   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Photosystem II Protein Complex MeSH
• Herbicides MeSH
• Naphthalenes MeSH

A library of novel 4-{[(benzyloxy)carbonyl]amino}-2-hydroxybenzoic acid amides was designed and synthesized in order to provide potential acetyl- and butyrylcholinesterase (AChE/BChE) inhibitors; the in vitro inhibitory profile and selectivity index were specified. Benzyl (3-hydroxy-4-{[2-(trifluoromethoxy)phenyl]carbamoyl}phenyl)carbamate was the best AChE inhibitor with the inhibitory concentration of IC50 = 36.05 µM in the series, while benzyl {3-hydroxy-4-[(2-methoxyphenyl)carbamoyl]phenyl}-carbamate was the most potent BChE inhibitor (IC50 = 22.23 µM) with the highest selectivity for BChE (SI = 2.26). The cytotoxic effect was evaluated in vitro for promising AChE/BChE inhibitors. The newly synthesized adducts were subjected to the quantitative shape comparison with the generation of an averaged pharmacophore pattern. Noticeably, three pairs of fairly similar fluorine/bromine-containing compounds can potentially form the activity cliff that is manifested formally by high structure-activity landscape index (SALI) numerical values. The molecular docking study was conducted for the most potent AChE/BChE inhibitors, indicating that the hydrophobic interactions were overwhelmingly generated with Gln119, Asp70, Pro285, Thr120, and Trp82 aminoacid residues, while the hydrogen bond (HB)-donor ones were dominated with Thr120. π-stacking interactions were specified with the Trp82 aminoacid residue of chain A as well. Finally, the stability of chosen liganded enzymatic systems was assessed using the molecular dynamic simulations. An attempt was made to explain the noted differences of the selectivity index for the most potent molecules, especially those bearing unsubstituted and fluorinated methoxy group.

• Keywords
• 4-aminosalicylanilides, CoMSA, carbamate synthesis, cholinesterase inhibition, lipophilicity, molecular docking, similarity-activity landscape index,
• MeSH
• Acetylcholinesterase chemistry   metabolism   MeSH
• Principal Component Analysis MeSH
• Butyrylcholinesterase chemistry   metabolism   MeSH
• Cholinesterase Inhibitors chemical synthesis   chemistry   MeSH
• Inhibitory Concentration 50 MeSH
• Carbamates pharmacology   MeSH
• Aminosalicylic Acid chemistry   MeSH
• Humans MeSH
• Ligands MeSH
• Models, Molecular MeSH
• Cell Line, Tumor MeSH
• Drug Design MeSH
• Solvents MeSH
• Cluster Analysis MeSH
• Molecular Dynamics Simulation MeSH
• Molecular Docking Simulation * MeSH
• THP-1 Cells MeSH
• Cell Survival MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Butyrylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• Carbamates MeSH
• Aminosalicylic Acid MeSH
• Ligands MeSH
• Solvents MeSH

A series of twenty-two novel N-(disubstituted-phenyl)-3-hydroxynaphthalene- 2-carboxamide derivatives was synthesized and characterized as potential antimicrobial agents. N-[3,5-bis(trifluoromethyl)phenyl]- and N-[2-chloro-5-(trifluoromethyl)phenyl]-3-hydroxy- naphthalene-2-carboxamide showed submicromolar (MICs 0.16-0.68 µM) activity against methicillin-resistant Staphylococcus aureus isolates. N-[3,5-bis(trifluoromethyl)phenyl]- and N-[4-bromo-3-(trifluoromethyl)phenyl]-3-hydroxynaphthalene-2-carboxamide revealed activity against M. tuberculosis (both MICs 10 µM) comparable with that of rifampicin. Synergistic activity was observed for the combinations of ciprofloxacin with N-[4-bromo-3-(trifluoromethyl)phenyl]- and N-(4-bromo-3-fluorophenyl)-3-hydroxynaphthalene-2-carboxamides against MRSA SA 630 isolate. The similarity-related property space assessment for the congeneric series of structurally related carboxamide derivatives was performed using the principal component analysis. Interestingly, different distribution of mono-halogenated carboxamide derivatives with the -CF3 substituent is accompanied by the increased activity profile. A symmetric matrix of Tanimoto coefficients indicated the structural dissimilarities of dichloro- and dimetoxy-substituted isomers from the remaining ones. Moreover, the quantitative sampling of similarity-related activity landscape provided a subtle picture of favorable and disallowed structural modifications that are valid for determining activity cliffs. Finally, the advanced method of neural network quantitative SAR was engaged to illustrate the key 3D steric/electronic/lipophilic features of the ligand-site composition by the systematic probing of the functional group.

• Keywords
• CoMSA, IVE-PLS, MIC, MTT assay, antistaphylococcal activity, antitubercular activity, hydroxynaphthalenecarboxamides, lipophilicity, similarity-activity landscape index,
• MeSH
• Anti-Infective Agents chemical synthesis   MeSH
• Methicillin-Resistant Staphylococcus aureus * MeSH
• Microbial Sensitivity Tests MeSH
• Mycobacterium tuberculosis * MeSH
• Naphthalenes chemistry   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Infective Agents MeSH
• Naphthalenes MeSH
• naphthalene-2-carboxamide MeSH Browser