Trifluoromethylcinnamanilide Michael Acceptors for Treatment of Resistant Bacterial Infections.

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.

Study of Biological Activities and ADMET-Related Properties of Salicylanilide-Based Peptidomimetics.

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.

Antistaphylococcal Activities and ADME-Related Properties of Chlorinated Arylcarbamoylnaphthalenylcarbamates.

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.

Study of Biological Activities and ADMET-Related Properties of Novel Chlorinated N-arylcinnamamides.

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.

Consensus-Based Pharmacophore Mapping for New Set of N-(disubstituted-phenyl)-3-hydroxyl-naphthalene-2-carboxamides.

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.

Biological Activities and ADMET-Related Properties of Novel Set of Cinnamanilides.

A series of nineteen novel ring-substituted N-arylcinnamanilides was synthesized and characterized. All investigated compounds were tested against Staphylococcus aureus as the reference strain, two clinical isolates of methicillin-resistant S. aureus (MRSA), and Mycobacterium tuberculosis. (2E)-N-[3-Fluoro-4-(trifluoromethyl)phenyl]-3-phenylprop-2-enamide showed even better activity (minimum inhibitory concentration (MIC) 25.9 and 12.9 µM) against MRSA isolates than the commonly used ampicillin (MIC 45.8 µM). The screening of the cell viability was performed using THP1-Blue™ NF-κB cells and, except for (2E)-N-(4-bromo-3-chlorophenyl)-3-phenylprop-2-enamide (IC50 6.5 µM), none of the discussed compounds showed any significant cytotoxic effect up to 20 µM. Moreover, all compounds were tested for their anti-inflammatory potential; several compounds attenuated the lipopolysaccharide-induced NF-κB activation and were more potent than the parental cinnamic acid. The lipophilicity values were specified experimentally as well. In addition, in silico approximation of the lipophilicity values was performed employing a set of free/commercial clogP estimators, corrected afterwards by the corresponding pKa calculated at physiological pH and subsequently cross-compared with the experimental parameters. The similarity-driven property space evaluation of structural analogs was carried out using the principal component analysis, Tanimoto metrics, and Kohonen mapping.

Insight into antimicrobial activity of substituted phenylcarbamoyloxypiperazinylpropanols.

3-[4-(Substituted)phenyl-/4-(diphenylmethyl)phenylpiperazin-1-yl]-2-hydroxypropyl-1-[(substituted)phenyl]carbamates and their salts with hydrochloric acid were synthesized, characterized, and tested in vitro against Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 as reference and quality control strains, against three methicillin-resistant isolates of S. aureus, and three isolates of vancomycin-resistant E. faecalis. All the compounds were evaluated against Mycobacterium tuberculosis H37Ra/ATCC 25177, M. kansasii DSM 44162, and M. smegmatis ATCC 700084. All of the tested compounds demonstrated very good activity against all the tested strains/isolates comparable with or better than that of clinically used drugs (ampicillin, ciprofloxacin, vancomycin, isoniazid). 1-[{(3-Trifluoromethyl)phenyl}carbamoyloxy-2-hydroxypropyl]-4-(3,4-dichlorophenyl)piperazin-1-ium chloride demonstrated the highest potency against all the tested strains/isolates (MICs ranged from 3.78 to 30.2 µM), and 1-[{(3-trifluoromethyl)phenyl}carbamoyloxy-2-hydroxypropyl]-4-(diphenylmethyl)piperazin-1-ium chloride was the most effective against all the screened mycobacterial strains (MICs ranged from 3.64 to 14.5 µM). All the investigated derivatives had strong antibiofilm activity against S. aureus ATCC 29123 and a synergistic or additive effect with gentamicin against isolates of E. faecalis with both intrinsic and acquired resistance to gentamicin. The screening of the cytotoxicity of the compounds was performed using human monocytic leukemia THP-1 cells. The IC50 values of the most effective compounds ranged from ca. 2.8 to 7.3 µM; thus, it can be stated that the antimicrobial effect is closely connected with their cytotoxicity. These observations disqualify these compounds from further development as antimicrobial agents, but they can be considered potential multi-target drugs with a preferred anticancer effect with good water solubility and additional anti-infectious activity.

Multiple In vitro biological effects of phenolic compounds from Morus alba root bark.

ETHNOPHARMACOLOGICAL RELEVANCE: Morus alba L. is used in traditional Chinese medicine for the treatment of various diseases, including bacterial infections and inflammation. As a rich source of phenolic compounds, the plant is an object of many phytochemical and pharmacological studies. AIM OF THE STUDY: The aim of the study was to isolate and evaluate possible parallel antiviral, antibacterial, and anti-inflammatory activities of phenolic mulberry compounds. MATERIALS AND METHODS: Extensive chromatographic separation of mulberry root bark extract and in vitro biological screening of 26 constituents identified promising candidates for further pharmacological research. Selected compounds were screened for anti-infective and anti-inflammatory activities. Antiviral activity was determined by the plaque number reduction assay and by the titer reduction assay, antibacterial using broth microdilution method, and anti-inflammatory activity using COX Colorimetric inhibitor screening assay kit. One compound was evaluated in vivo in carrageenan-induced paw-edema in mice. RESULTS: Five prenylated compounds 1, 2, 8, 9, and 11, together with a simple phenolic ester 13, exhibited inhibitory activity against the replication of herpes simplex virus 1 (HSV-1) or herpes simplex virus 2 (HSV-2), with IC50 values ranging from 0.64 to 1.93 µg/mL, and EC50 values 0.93 and 1.61 µg/mL. Molecular docking studies demonstrated the effects of the active compounds by targeting HSV-1 DNA polymerase and HSV-2 protease. In antibacterial assay, compounds 1, 4, 11, and 17 diminished the growth of all of the Gram-positive strains tested, with MIC values of 1-16 µg/mL. The anti-inflammatory ability of several compounds to inhibit cyclooxygenase 2 (COX-2) was tested in vitro, and compound 16 displayed greater activity than the indomethacin, positive control. Mulberrofuran B (11) showed anti-inflammatory activity in vivo against carrageenan-induced paw-edema in mice. CONCLUSIONS: Experimental investigation showed promising antiviral, antibacterial, and/or anti-inflammatory activities of the phenolic mulberry constituents, often with multiple inhibitory effects that might be used as a potential source of new medicine.

Bioactivity of Methoxylated and Methylated 1-Hydroxynaphthalene-2-Carboxanilides: Comparative Molecular Surface Analysis.

A series of twenty-six methoxylated and methylated N-aryl-1-hydroxynaphthalene- 2-carboxanilides was prepared and characterized as potential anti-invasive agents. The molecular structure of N-(2,5-dimethylphenyl)-1-hydroxynaphthalene-2-carboxamide as a model compound was determined by single-crystal X-ray diffraction. All the analysed compounds were tested against the reference strain Staphylococcus aureus and three clinical isolates of methicillin-resistant S. aureus as well as against Mycobacterium tuberculosis and M. kansasii. In addition, the inhibitory profile of photosynthetic electron transport in spinach (Spinacia oleracea L.) chloroplasts was specified. In vitro cytotoxicity of the most effective compounds was tested on the human monocytic leukaemia THP-1 cell line. The activities of N-(3,5-dimethylphenyl)-, N-(3-fluoro-5-methoxy-phenyl)- and N-(3,5-dimethoxyphenyl)-1-hydroxynaphthalene-2-carbox- amide were comparable with or even better than the commonly used standards ampicillin and isoniazid. All promising compounds did not show any cytotoxic effect at the concentration >30 µM. Moreover, an in silico evaluation of clogP features was performed for the entire set of the carboxamides using a range of software lipophilicity predictors, and cross-comparison with the experimentally determined lipophilicity (log k), in consensus lipophilicity estimation, was conducted as well. Principal component analysis was employed to illustrate noticeable variations with respect to the molecular lipophilicity (theoretical/experimental) and rule-of-five violations. Additionally, ligand-oriented studies for the assessment of the three-dimensional quantitative structure-activity relationship profile were carried out with the comparative molecular surface analysis to determine electron and/or steric factors that potentially contribute to the biological activities of the investigated compounds.

Second generation of primaquine ureas and bis-ureas as potential antimycobacterial agents.

Here, we describe design and synthesis of twelve novel compounds bearing primaquine motif and hydroxy- or halogenamine linked by an urea or bis-urea spacer. Preparation of ureas 3a-f started with the conversion of primaquine to benzotriazolide 2 and aminolysis of the later compound by 4-(2-aminoethyl)phenol or amino alcohols bearing fluorine atom, cycloalkyl or trifluoromethyl group under microwave irradiation. The four-step sequence leading to bis-ureas 6a-f included preparation of benzotriazolide 2 and two intermediates, semicarbazide 4 and benzotriazole bis-urea 5, which upon aminolysis with the same aminophenol or amino alcohols gave the title compounds. Antimycobacterial screening detected three active compounds against Mycobacterium marinum and M. tuberculosis, namely 3b, 3f and 6f, derived from cyclobutyl amino alcohol or amino phenol.

Dibasic Derivatives of Phenylcarbamic Acid against Mycobacterial Strains: Old Drugs and New Tricks?

In order to provide a more detailed view on the structure⁻antimycobacterial activity relationship (SAR) of phenylcarbamic acid derivatives containing two centers of protonation, 1-[2-[({[2-/3-(alkoxy)phenyl]amino}carbonyl)oxy]-3-(dipropylammonio)propyl]pyrrolidinium oxalates (1a⁻d)/dichlorides (1e⁻h) as well as 1-[2-[({[2-/3-(alkoxy)phenyl]amino}carbonyl)oxy]-3-(di-propylammonio)propyl]azepanium oxalates (1i⁻l)/dichlorides (1m⁻p; alkoxy = butoxy to heptyloxy) were physicochemically characterized by estimation of their surface tension (γ; Traube's stalagmometric method), electronic features (log ε; UV/Vis spectrophotometry) and lipophilic properties (log kw; isocratic RP-HPLC) as well. The experimental log kw dataset was studied together with computational logarithms of partition coefficients (log P) generated by various methods based mainly on atomic or combined atomic and fragmental principles. Similarities and differences between the experimental and in silico lipophilicity descriptors were analyzed by unscaled principal component analysis (PCA). The in vitro activity of compounds 1a⁻p was inspected against Mycobacterium tuberculosis CNCTC My 331/88 (identical with H37Rv and ATCC 2794, respectively), M. tuberculosis H37Ra ATCC 25177, M. kansasii CNCTC My 235/80 (identical with ATCC 12478), the M. kansasii 6509/96 clinical isolate, M. kansasii DSM 44162, M. avium CNCTC My 330/80 (identical with ATCC 25291), M. smegmatis ATCC 700084 and M. marinum CAMP 5644, respectively. In vitro susceptibility of the mycobacteria to reference drugs isoniazid, ethambutol, ofloxacin or ciprofloxacin was tested as well. A very unique aspect of the research was that many compounds from the set 1a⁻p were highly efficient almost against all tested mycobacteria. The most promising derivatives showed MIC values varied from 1.9 µM to 8 µM, which were lower compared to those of used standards, especially if concerning ability to fight M. tuberculosis H37Ra ATCC 25177, M. kansasii DSM 44162 or M. avium CNCTC My 330/80. Current in vitro biological assays and systematic SAR studies based on PCA approach as well as fitting procedures, which were supported by relevant statistical descriptors, proved that the compounds 1a⁻p represented a very promising molecular framework for development of 'non-traditional' but effective antimycobacterial agents.

Synthesis and Spectrum of Biological Activities of Novel N-arylcinnamamides.

: A series of sixteen ring-substituted N-arylcinnamamides was prepared and characterized. Primary in vitro screening of all the synthesized compounds was performed against Staphylococcus aureus, three methicillin-resistant S. aureus strains, Mycobacterium tuberculosis H37Ra, Fusarium avenaceum, and Bipolaris sorokiniana. Several of the tested compounds showed antistaphylococcal, antitubercular, and antifungal activities comparable with or higher than those of ampicillin, isoniazid, and benomyl. (2E)-N-[3,5-bis(trifluoromethyl)phenyl]-3-phenylprop-2-enamide and (2E)-3-phenyl-N-[3-(trifluoromethyl)phenyl]prop-2-enamide showed the highest activities (MICs = 22.27 and 27.47 µM, respectively) against all four staphylococcal strains and against M.tuberculosis. These compounds showed an activity against biofilm formation of S.aureus ATCC 29213 in concentrations close to MICs and an ability to increase the activity of clinically used antibiotics with different mechanisms of action (vancomycin, ciprofloxacin, and tetracycline). In time-kill studies, a decrease of CFU/mL of >99% after 8 h from the beginning of incubation was observed. (2E)-N-(3,5-Dichlorophenyl)- and (2E)-N-(3,4-dichlorophenyl)-3-phenylprop-2-enamide had a MIC = 27.38 µM against M. tuberculosis, while a significant decrease (22.65%) of mycobacterial cell metabolism determined by the MTT assay was observed for the 3,5-dichlorophenyl derivative. (2E)-N-(3-Fluorophenyl)- and (2E)-N-(3-methylphenyl)-3-phenylprop-2-enamide exhibited MICs = 16.58 and 33.71 µM, respectively, against B. sorokiniana. The screening of the cytotoxicity of the most effective antimicrobial compounds was performed using THP-1 cells, and these chosen compounds did not shown any significant lethal effect. The compounds were also evaluated for their activity related to the inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. (2E)-N-(3,5-dichlorophenyl)-3-phenylprop-2-enamide (IC50 = 5.1 µM) was the most active PET inhibitor. Compounds with fungicide potency did not show any in vivo toxicity against Nicotiana tabacum var. Samsun. The structure⁻activity relationships are discussed.

Asymmetric Primaquine and Halogenaniline Fumardiamides as Novel Biologically Active Michael Acceptors.

Novel primaquine (PQ) and halogenaniline asymmetric fumardiamides 4a⁻f, potential Michael acceptors, and their reduced analogues succindiamides 5a⁻f were prepared by simple three-step reactions: coupling reaction between PQ and mono-ethyl fumarate (1a) or mono-methyl succinate (1b), hydrolysis of PQ-dicarboxylic acid mono-ester conjugates 2a,b to corresponding acids 3a,b, and a coupling reaction with halogenanilines. 1-[bis(Dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU) was used as a coupling reagent along with Hünig's base. Compounds 4 and 5 were evaluated against a panel of bacteria, several Mycobacterium strains, fungi, a set of viruses, and nine different human tumor cell lines. p-Chlorofumardiamide 4d showed significant activity against Staphylococcus aureus,Streptococcus pneumoniae and Acinetobacter baumannii, but also against Candida albicans (minimum inhibitory concentration (MIC) 6.1⁻12.5 µg/mL). Together with p-fluoro and p-CF3 fumardiamides 4b,f, compound 4d showed activity against Mycobacterium marinum and 4b,f against M. tuberculosis. In biofilm eradication assay, most of the bacteria, particularly S. aureus, showed susceptibility to fumardiamides. m-CF3 and m-chloroaniline fumardiamides 4e and 4c showed significant antiviral activity against reovirus-1, sindbis virus and Punta Toro virus (EC50 = 3.1⁻5.5 µM), while 4e was active against coxsackie virus B4 (EC50 = 3.1 µM). m-Fluoro derivative 4a exerted significant cytostatic activity (IC50 = 5.7⁻31.2 µM). Acute lymphoblastic leukemia cells were highly susceptible towards m-substituted derivatives 4a,c,e (IC50 = 6.7⁻8.9 µM). Biological evaluations revealed that fumardiamides 4 were more active than succindiamides 5 indicating importance of Michael conjugated system.

In vitro activity of salicylamide derivatives against vancomycin-resistant enterococci.

A series of 13 salicylamide derivatives was assessed for antibacterial activity against three isolates of vancomycin-resistant Enterococcus faecalis (VRE) and Enterococcus faecalis ATCC 29212 as a quality standard. The minimum inhibitory concentration was determined by the broth microdilution method with subsequent subcultivation of aliquots to assess minimum bactericidal concentration. The growth kinetics was established by the time-kill assay. Ampicillin, ciprofloxacin, tetracycline and vancomycin were used as the reference antibacterial drugs. Three of the investigated compounds showed strong bacteriostatic activity against VRE (0.199-25 µM) comparable to or more potent than ampicillin and ciprofloxacin. In addition, these compounds were tested for synergistic effect with vancomycin, ciprofloxacin and tetracycline, while 5-chloro-2-hydroxy-N-[4-(trifluoromethyl)phenyl]benzamide showed the highest potency as well as synergistic activity with vancomycin against VRE 368. Screening of the cytotoxicity of the most effective compounds was performed using human monocytic leukemia THP-1 cells, and based on LD50 values, it can be stated that the compounds have insignificant toxicity against human cells.