Vladimír Garaj

This research aimed to evaluate structural, physicochemical and pharmacokinetic characteristics of racemic 2-hydroxy-3-(4-phenylpiperazin-1-yl)propyl 4-[(alkoxycarbonyl)amino]benzoates (Ib)–(IVb) and 2-hydroxy-3-[4-(R-substituted phenyl)piperazin-1-yl]propyl 4-[(alkoxycarbonyl)amino]benzoates (1b)–(12b), while further extending the in vitro screening of their racemic salts, 1-(3-{4-[(alkoxycarbonyl)amino]benzoyloxy}-2-hydroxypropyl)-4-(R-substituted phenyl)piperazin-1-ium chlorides (I)–(IV) and (1)–(12) (alkoxy = methoxy to butoxy in all of these series, and R = H, 4′-F, 2′-F or 2′-OCH₃), against several mycobacterial species, including a slow-growing virulent Mycobacterium tuberculosis (Mtb) H₃₇R_v strain. The values of structural, physicochemical and several pharmacokinetic descriptors of the compounds (Ib)–(IVb) and (1b)–(12b) were generated in silico, employing a palette of interactive web-based engines and standalone software packages. The obtained data allowed for exploration of their mutual relationships through a chemometric principal component analysis method. The predicted outputs were compared to the values of respective descriptors defining antimycobacterial drugs approved worldwide for therapeutic use in human medicine. Molecular docking (MD) analyses were carried out to explore the possibilities of whether particular (R)- and (S)-stereoisomers of non-protonated derivatives, as well as (R)- and (S)-stereoisomeric forms of their salts (I)–(IV) and (1)–(12) would effectively interact with a proposed pharmacological target, adenosine 5′-triphosphate (ATP) synthase. This membrane–protein complex was considered essential for energy metabolism and survival of various mycobacterial species. Respecting the fundamental structural arrangement of more efficient salts, the importance of their structural and spatial features was highlighted to achieve relative effective interactions with particular subunits of ATP synthase present in Mtb H₃₇R_v. The results of the MD evaluations could contribute to the understanding of how these compounds inhibited growth of Mtb H₃₇R_v. 1-(3-{4-[(Butoxycarbonyl)amino]benzoyloxy}-2-hydroxypropyl)-4-phenylpiperazin-1-ium chloride (IV) with a minimum inhibitory concentration (MIC) value of 62.5 μM estimated in vitro and 1-(3-{4-[(butoxycarbonyl)amino]benzoyloxy}-2-hydroxypropyl)-4-(2-methoxyphenyl)piperazin-1-ium chloride (12) with MIC = 16 μM, as the most effective anti-Mtb H₃₇R_v agents of each series of the salts, were screened in vitro to investigate their antiproliferative or (eventual) cytotoxic properties using a normal human dermal fibroblast cell line. The derivative (IV) decreased cell viability slightly more compared to the molecule (12).

A series of 1,3,5-triazinyl aminobenzenesulfonamides substituted by aminoalcohol, aminostilbene, and aminochalcone structural motifs was synthesized as potential human carbonic anhydrase (hCA) inhibitors. The compounds were evaluated on their inhibition of tumor-associated hCA IX and hCA XII, hCA VII isoenzyme present in the brain, and physiologically important hCA I and hCA II. While the test compounds had only a negligible effect on physiologically important isoenzymes, many of the studied compounds significantly affected the hCA IX isoenzyme. Several compounds showed activity against hCA XII; (E)-4-{2-[(4-[(2,3-dihydroxypropyl)amino]-6-[(4-styrylphenyl)amino]-1,3,5-triazin-2-yl)amino]ethyl}benzenesulfonamide (31) and (E)-4-{2-[(4-[(4-hydroxyphenyl)amino]-6-[(4-styrylphenyl)amino]-1,3,5-triazin-2-yl)amino]ethyl}benzenesulfonamide (32) were the most effective inhibitors with K_Is = 4.4 and 5.9 nM, respectively. In addition, the compounds were tested against vancomycin-resistant Enterococcus faecalis (VRE) isolates. (E)-4-[2-({4-[(4-cinnamoylphenyl)amino]-6-[(4-hydroxyphenyl)amino]-1,3,5-triazin-2-yl}amino)ethyl]benzenesulfonamide (21) (MIC = 26.33 µM) and derivative 32 (MIC range 13.80–55.20 µM) demonstrated the highest activity against all tested strains. The most active compounds were evaluated for their cytotoxicity against the Human Colorectal Tumor Cell Line (HCT116 p53 +/+). Only 4,4’-[(6-chloro-1,3,5-triazin-2,4-diyl)bis(iminomethylene)]dibenzenesulfonamide (7) and compound 32 demonstrated an IC₅₀ of ca. 6.5 μM; otherwise, the other selected derivatives did not show toxicity at concentrations up to 50 µM. The molecular modeling and docking of active compounds into various hCA isoenzymes, including bacterial carbonic anhydrase, specifically α-CA present in VRE, was performed to try to outline a possible mechanism of selective anti-VRE activity.

The photoswitching properties of three readily accesible benzoylpyridine hydrazones were investigated. Interestingly, replacing classical stirring with ultrasound wave activation results in pure thermodynamically less stable E isomer crystallization at room temperature. The studied benzoylpyridine hydrazones exhibit both P- and T-photochromic behaviour, depending on the benzoyl substituent, and improved addressability compared to most of the previously published pyridyl based hydrazones and 2-pyridylcarboxaldehyde acylhydrazones. Low activation entropy and calculated transition state geometry favour the inversion mechanism of their thermal isomerization rather than tautomerization followed by rotation recently found for pyridyl-hydrazone ester or nitrile rotary switches. The association behaviour of the nitro derivative during its thermal E-to-Z isomerization in highly polar DMSO indicates an important role of intermolecular hydrogen bonding in the thermal kinetics of benzoylpyridine-based hydrazone photoswitches. Moreover, the addition of triethylamine significantly accelerates the rate of Z-isomer thermal isomerization from days to seconds and could thus pave the way to fast pyridyl hydrazone T-type photochromic compounds in polar solvents. This study could therefore contribute to general knowledge related to the photochromic behaviour of hydrazones as an important class of modern photoswitches.

Sulfonamides incorporating 1,3,5-triazine moieties can selectively and potently inhibit carbonic anhydrase transmembrane isoforms IX, XII, and XIV over cytosolic isoforms I and II. In the present work, a highly effective synthetic procedure was proposed for this group of potent cancerostatic drugs and compared with previously used methods. The synthesis of triazinyl-substituted benzene-sulfonamide conjugates with amino acids can be easily carried out using sodium carbonate-based water solution as a synthetic medium instead of N,N-Diisopropylethylamine/Dimethylformamide. The benefits of this synthetic procedure include: (i) high selectivity of the creation of disubstituted conjugates; (ii) several times higher yield (≥95%) than that achieved previously; (iii) elimination of organic solvents by the use of an environmental friendly water medium (green chemistry); (iv) simple and fast isolation of the product. The synthesis and resulting products were evaluated using TLC, IR, NMR, and MS methods. The present work demonstrates a significant advantage in providing shortened routes to target structures.

The water sensing properties of two efficient two-component fluorescent “turn-on” chemo-sensors based on the 7-dialkylaminocoumarin oxime acid-base equilibrium were investigated. Interestingly, although simple frontier orbital analysis predicts an intramolecular photoinduced electron transfer quenching pathway in conjugated oximates, TD-DFT (Time-dependent density functional theory) quantum chemical calculations support non-radiative dark S₁ excited state deactivation as a fluorescence quenching mechanism. Due to the acid-base sensing mechanism and sensitive “turn-on” fluorescent response, both studied coumarin aldoxime chemosensors exhibit rapid response to low-level water content in polar aprotic solvents, with detection limits comparable to chemodosimeters or chemosensors based on interpolymer π-stacking aggregation.

Combinatorial library of novel benzenesulfonamides was docked (Schrodinger Glide) into mycobacterial carbonic anhydrase (mtCA II) and human (hCA II) isoforms with an aim to find drug candidates with selective activity on mtCA II. The predicted selectivity was calculated based on optimized MM-GBSA free energies for ligand enzyme interactions. Selectivity, LogP (o/w) and interaction energy were used to calculate the selection index which determined the subset of best scoring molecules selected for further evaluation. Structure-activity relationship was found for fragment subsets, showing us the possible way regarding how to influence lipophilicity without affecting ligand-enzyme binding properties.

The water sensing properties of four new efficient two-component colorimetric and fluorescent “turn-on” chemosensors based on the coumarin phenylsemicarbazone skeleton bearing different acceptor/donor functional groups on aniline structural subunits were investigated and are discussed in terms of their photophysical properties, interaction mechanism, sensitivity and substituent effects. Due to the sensing mechanism based on reversible acid–base keto/enolate (hydrazide/hydrazonolate) equilibrium, all the studied coumarin phenylsemicarbazone chemosensors provided rapid and reversible response to low-level water content in polar aprotic solvents. To the best of our knowledge, the determined detection limits for water by studied chemosensors are among the lowest published detection limits in the literature and have competitive sensitivity with chemodosimeters. Their deficiency is, however, the necessity of F⁻ base presence.

A series of alkylamino derivatives of N-benzylpyrazine-2-carboxamide was designed, synthesized and assayed in vitro for their antimycobacterial, antibacterial, antifungal as well as antiviral activities. Final structures were prepared from 6-chloro (1), 5-chloro (2) or 3-chloro (3) derivatives of N-benzylpyrazine-2-carboxamide by nucleophilic substitution of chlorine with n-alkylamines in the range from butylamine to octylamine (labelled a–e). Series 1a–e and 2a–e exerted higher activity against Mycobacterium tuberculosis H37Rv compared to the corresponding pattern compounds and the reference compound pyrazinamide. The most active derivatives reached an activity MIC = 4.6–10 μM (M. tbc H37Rv). More importantly, activity was also observed against other tested mycobacterial strains (including drug-resistant strains). Substitution of 3-chlorine was disadvantageous and led to completely inactive compounds 3a–e. Some compounds showed activity against Gram-positive bacterial strains (including MRSA) or influenza virus, but no antifungal activity was observed.