Vladimír Garaj

Sulfonamides incorporating 1,3,5-triazine moieties selectively and potently inhibit carbonic anhydrase transmembrane isoforms IX, XII and XIV over cytosolic isoforms I and II: Solution and X-ray crystallographic studies.

Reaction of cyanuryl chloride with d,l-amino acids and amino alcohols afforded a new series of triazinyl-substituted benzenesulfonamides incorporating amino acyl/hydroxyalkyl-amino moieties. Inhibition studies of physiologically relevant human carbonic anhydrase (CA, EC 4.2.1.1) isoforms, such as CA I, II, IX, XII and XIV with these compounds are reported. They showed moderate-weak inhibition of the cytosolic, offtarget isozymes CA I and II, but many of them were low nanomolar inhibitors of the transmembrane, tumor-associated CA IX and XII (and also of CA XIV). The X-ray crystal structure of two of these compounds in adduct with CA II allowed us to understand the features associated with this strong inhibitory properties and possibly also their selectivity. Two of these compounds were also investigated for the inhibition of other human isoforms, that is, hCA IV, VA, VB, VI, VII and XIII, as well as inhibitors of the fungal pathogenic CAs Nce103 (Candida albicans) and Can2 (Cryptococcus neoformans), showing interesting activity. The 1,3,5-triazinyl-substituted benzenesulfonamides constitute thus a class of compounds with great potential for obtaining inhibitors targeting both α-class mammalian, tumor-associated, and β-class from pathogenic organisms CAs.

Thermodynamics of binding of Zn2+ to carbonic anhydrase inhibitors

The Becke3LYP functional of DFT theory and the two-layered ONIOM (B3LYP/6–311 + G(d,p): MNDO) method were used to characterize 46 gas-phase complexes of 34 neutral and anionic ligands (H2O, CH3OH, CH3COOH, CH3CONH2, HOSO2NH2, CO2, HSO2NH2, CH3SO2NH2, CH3C(= O)NHOH, imidazole, NH2SO2NH2, anions of 4-aminobenzenesulphonamide, saccharin, 1I9L, brinzolamide, dorzolamide, acetazolamide, further HO(−), CH3CO(−), CH3COO(−), CH3CONH(−), N = N = N(−), S = C = N(−), CH3C(= O)NHO(−), HOCOO(−), imidazoleN(−), phenol-O(−), HOSO2NH(−), (−)OSO2NH(−), (−)OSO2NH2, H2NSO2NH(−), HSO2NH(−), CH3SO2NH(−), and CF3SO2NH(−), respectively) with Zn2+. Proton dissociation enthalpies and Gibbs energies of acidic inhibitors in the presence of zinc were computed. Their gas-phase acidity considerably increases upon chelation. Of the bases investigated, the weakest zinc affinity is exhibited by carbon dioxide (- 313.5 kJ mol−1). Deprotonated inhibitors have higher affinities for zinc than the neutral ones. Compared to the other mono-deprotonated ligands the acetohydroxamic acid anion has the highest affinity for zinc (- 1872.7 kJ mol−1). The zinc affinity of the acetazolamide anion computed using the hybrid ONIOM (B3LYP/6-311 + G(d,p): MNDO) method is in very good agreement with the full DFT ones and this method can be adopted to model large complexes of inhibitors with the active site of carbonic anhydrase.

Optimal detection of cholinesterase activity in biological samples: Modifications to the standard Ellman’s assay

Ellmans assay is the most commonly used method to measure cholinesterase activity. It is cheap, fast, and reliable, but it has limitations when used for biological samples. The problems arise from 5,5-dithiobis(2-nitrobenzoic acid) (DTNB), which is unstable, interacts with free sulfhydryl groups in the sample, and may affect cholinesterase activity. We report that DTNB is more stable in 0.09 M Hepes with 0.05 M sodium phosphate buffer than in 0.1M sodium phosphate buffer, thereby notably reducing background. Using enzyme-linked immunosorbent assay (ELISA) to enrich tissue homogenates for cholinesterase while depleting the sample of sulfhydryl groups eliminates unwanted interactions with DTNB, making it possible to measure low cholinesterase activity in biological samples. To eliminate possible interference of DTNB with enzyme hydrolysis, we introduce a modification of the standard Ellmans assay. First, thioesters are hydrolyzed by cholinesterase to produce thiocholine in the absence of DTNB. Then, the reaction is stopped by a cholinesterase inhibitor and the produced thiocholine is revealed by DTNB and quantified at 412 nm. Indeed, this modification of Ellmans method increases butyrylcholinesterase activity by 20 to 25%. Moreover, high stability of thiocholine enables separation of the two reactions of the Ellmans method into two successive steps that may be convenient for some applications.

The inhibitory potency of local anesthetics on NMDA receptor signalling depends on their structural features.

Development of postoperative hyperalgesia depends on N-methyl-d-aspartate (NMDA) receptor activation. Local anesthetics protect against those hyperalgesic pain states and inhibit NMDA receptor activation. To outline what structural features of local anesthetics are responsible for NMDA receptor inhibition we evaluated a series of experimental lidocaine analogs (carbanilic derivates). Human GluN1/GluN2A NMDA receptors were expressed recombinantly in Xenopus laevis oocytes. Peak currents were measured by voltage clamp technique. Oocytes were stimulated with glutamate/glycine (EC(50)). The responses following a 10min incubation with in total 13 experimental derivates of local anesthetics (10(-3)M-10(-7)M) were measured to obtain the IC(50). Furthermore the Comprehensive Descriptors for Structural and Statistical Analysis CODESSA software was used to design a Quantitative Structure-Activity Relationship (QSAR)-model for all substances. The IC(50) values were in the range of 2.74×10(-5)M-2.26×10(-3)M, strongly affected by the position and the length of the aliphatic side chain in the aromatic part of the local anesthetic molecule. Substance with no substituent on the aromatic ring showed the highest inhibitory activity. The obtained QSAR model predicted that lidocaine derivatives with free positions 2 and 6 on the aromatic ring had a higher efficacy than clinically used local anesthetics for inhibition of NMDA receptor signaling. Structural changes of local anesthetic molecules can alter the potency to inhibit NMDA receptor signaling and are independent of the local anesthetic (sodium-channel blocking) potency. The development of novel drugs based on local anesthetic like structures may be a new approach for the protection or treatment of NMDA receptor mediated hyperalgesia and may be associated with a low side effect profile.

Synthesis and antimycobacterial evaluation of 5-alkylamino-N-phenylpyrazine-2-carboxamides.

Substitution of chlorine in 5-chloro-N-phenylpyrazine-2-carboxamide (1) with simple n-alkylamines yielded a series of 5-alkylamino-N-phenylpyrazine-2-carboxamides (propylamino to octylamino derivatives), which possessed similar or increased activity against Mycobacterium tuberculosis H37Rv compared to parent 5-chloro derivative (1), with MIC ranging from 2.5 to 12.2 μM. 5-Butylamino to 5-heptylamino derivatives exerted similar activity also against Mycobacterium kansasii. Importantly, the substitution led also to significant decrease of in vitro cytotoxicity in HepG2 cell line. 5-Heptylamino-N-phenylpyrazine-2-carboxamide (1e) exerted MIC=2.5 μM (M.tbc) and IC50 >250 μM (HepG2). Further modification of alkylamino chain with terminal methoxy or hydroxy group lead to compounds with decreased or none activity, the decrease was proportional to the decrease of lipophilicity. 5-(2-Phenylethylamino) and 5-(3-phenylpropylamino) derivatives were also of decreased activity. On contrary to alkylamino derivatives derived from 1, alkylamino derivatives derived from 5-chloro-N-2-chlorophenylpyrazine-2-carboxamide (2) possessed substantially decreased or none activity. None of the prepared compounds was active against Mycobacterium avium.

Synthesis and Antimicrobial Evaluation of 6-Alkylamino-N-phenylpyrazine-2-carboxamides.

This work presents synthesis and antimicrobial evaluation of nineteen 6‐alkylamino‐N–phenylpyrazine‐2‐carboxamides. Antimycobacterial activity was determined against Mycobacterium tuberculosis H37Rv, M. kansasii and two strains of M. avium. Generally, the antimycobacterial activity increased with prolongation of simple alkyl chain and culminated in compounds with heptylamino substitution (3e, 4e) with MIC = 5–10 μm against M. tuberculosis H37Rv. On the contrary, derivatives with modified alkyl chain (containing e.g. terminal methoxy or hydroxy group) as well as phenylalkylamino derivatives were mainly inactive. The most active compounds (with hexyl to octylamino substitution) were evaluated for their in vitro activity against drug‐resistant strains of M. tuberculosis and possessed activity comparable to that of the reference drug isoniazid. None of the tested compounds were active against M. avium. Some derivatives exhibited activity against Gram‐positive bacteria including methicillin‐resistant Staphylococcus aureus (best MIC = 7.8 μm), while Gram‐negative strains as well as tested fungal strains were completely unsusceptible. Active compounds were tested for in vitro toxicity on various cell lines and in most cases were non‐toxic up to 100 μm.

Novel sulfonamide incorporating piperazine, aminoalcohol and 1,3,5-triazine structural motifs with carbonic anhydrase I, II and IX inhibitory action

A new series of s-triazine derivatives incorporating sulfanilamide, homosulfanilamide, 4-aminoethyl-benzenesulfonamide and piperazine or aminoalcohol structural motifs is reported. Molecular docking was exploited to select compounds from virtual combinatorial library for synthesis and subsequent biological evaluation. The compounds were prepared by using step by step nucleophilic substitution of chlorine atoms from cyanuric chloride (2,4,6-trichloro-1,3,5-triazine). The compounds were tested as inhibitors of physiologically relevant carbonic anhydrase (CA, EC 4.2.1.1) isoforms. Specifically, against the cytosolic hCA I, II and tumor-associated hCA IX. These compounds show appreciable inhibition. hCA I was inhibited with KIs in the range of 8.5-2679.1 nM, hCA II with KIs in the range of 4.8-380.5 nM and hCA IX with KIs in the range of 0.4-307.7 nM. As other similar derivatives, some of the compounds showed good or excellent selectivity ratios for inhibiting hCA IX over hCA II, of 3.5-18.5. 4-[({4-Chloro-6-[(4-hydroxyphenyl)amino]-1,3,5-triazin-2-yl}amino)methyl] benzene sulfonamide demonstrated subnanomolar affinity for hCA IX (0.4 nM) and selectivity (18.50) over the cytosolic isoforms. This series of compounds may be of interest for the development of new, unconventional anticancer drugs targeting hypoxia-induced CA isoforms such as CA IX.

Coumarin phenylsemicarbazones: sensitive colorimetric and fluorescent “turn-on” chemosensors for low-level water content in aprotic organic solvents

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.

Alkylamino derivatives of N-benzylpyrazine-2-carboxamide: synthesis and antimycobacterial evaluation

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.

Optimization and Comparison of Synthetic Procedures for a Group of Triazinyl-Substituted Benzene-Sulfonamide Conjugates with Amino Acids

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.