Magdalena Piętka-Ottlik

Synthesis and biological evaluation of new amino acid and dipeptide derivatives of neocryptolepine as anticancer agents.

The syntheses of neocryptolepine derivatives containing an amino acid or a dipeptide at the C-9 position and their evaluation for antitumor activity in vitro and in vivo are reported. To establish the influence of an amino acid or a peptide on the physicochemical properties of 5H-indolo[2,3-b]quinoline (DiMIQ), lipophilic and hemolytic properties were investigated. Most of the compounds displayed a high antiproliferative activity in vitro and strongly inhibited growth of tumor in mice compared to cyclophosphamide. The attachment of the hydrophilic amino acid or the peptide to the hydrophobic DiMIQ increased its hydrophilic properties and decreased its hemolytic activity. The glycylglycine conjugate (7a) was the most promising derivative. It strongly inhibited the growth of the tumor in mice (at dose 50 mg kg(-1) day(-1) it inhibited the tumor growth by 46-63% on days 11-16 and by 29-43% on days 18-23) and significantly decreased hemolytic activity and lowered the in vivo toxicity compared to DiMIQ.

Evaluation of the antifungal and plasma membrane H+-ATPase inhibitory action of ebselen and two ebselen analogs in S. cerevisiae cultures

The plasma membrane H+-ATPase pump (Pma1p) has been proposed as a viable target for antifungal drugs since this high capacity proton pump plays a critical role in the intracellular regulation of pH and in nutrient uptake of yeast and other fungi. In recent years, this and other laboratories have verified that the antifungal activity of 2-phenylbenzisoselenazol-3(2H)-one, an organoselenium compound commonly referred to as ebselen (1), stems, at least in part, from its inhibitory action on the fungal Pma1p. In the present study, the antifungal efficacy of 2-(3-pyridinyl)-benzisoselenazol-3(2H)-one (2) and 2-phenylbenzisoselenazol-3(2H)-one 1-oxide (3), two ebselen analogs, was evaluated using a strain of S. cerevisiae and compared against that of 1. In addition, the study also examined the inhibitory potential of these three compounds toward the Pma1p of S. cerevisiae. Based on mean IC50 values, the antifungal potency was found to decrease in the order 3u2009>u20091u2009>u20092. However, in terms of inhibitory action on Pma1p, the potency decreased in the order 1u2009>u20093u2009>u20092. The magnitude of these activities appears to be correlated with the corresponding log P values, with compound 2 being the most hydrophilic and the least active of the three.

Ecotoxicity and biodegradability of antielectrostatic dicephalic cationic surfactants.

Four series of dicephalic cationic surfactants, considered as new antielectrostatic agents have been investigated in order to establish their toxicity and biodegradability. Among them N,N-bis[3,3-(dimethylamine)propyl]alkylamides, N,N-bis[3,3-(dimethylamine)propyl]alkylamide dihydrochlorides, N,N-bis[3,3-(trimethylammonio)propyl]alkylamide dibromides and N,N-bis[3,3-(trimethylammonio)propyl]alkylamide dimethylsulphates with different hydrophobic chain length (n-C(9)H(19) to n-C(15)H(31)) and type of counterion (chloride, bromide and methylsulfate) have been studied. The inhibitory effect against microorganisms has been examined using model gram-positive and gram-negative bacteria, and yeasts. None of the tested surfactants have shown antimicrobial activity against gram-negative bacteria (Escherichia coli, Pseudomonas putida) and yeasts (Saccharomyces cerevisiae, Rhodotorula glutinis) at a concentration below 1000 μg mL(-1), however some of them were moderately active against gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis). The Microtox® test was successfully applied to measure EC(50) values of the studied dicephalic cationic surfactants. Their toxicity to Vibrio fischeri depended upon the alkanoyl chain length with the EC(50) values in a range of 2.6-980 mg L(-1). N,N-bis[3,3-(dimethylamine)propyl]alkylamide dihydrochlorides 2a-b and N,N-bis[3,3-(trimethylammonio)propyl]alkylamide dibromides 3a-b comprising n-decanoyl and n-dodecanoyl hydrophobic tails appeared to be the least toxic. Furthermore, the biodegradability under aerobic conditions of 2a-b, 3a-b was evaluated using OECD Method 301F. According to the obtained results 2a, 3a-3b can be considered as almost readily biodegradable and they are not expected to be persistent in the environment. Additionally, partial biodegradation was observed for 2b, indicating its possible biodegradation in wastewater treatment systems.

Ebselen, a Small-Molecule Capsid Inhibitor of HIV-1 Replication

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) capsid plays crucial roles in HIV-1 replication and thus represents an excellent drug target. We developed a high-throughput screening method based on a time-resolved fluorescence resonance energy transfer (HTS-TR-FRET) assay, using the C-terminal domain (CTD) of HIV-1 capsid to identify inhibitors of capsid dimerization. This assay was used to screen a library of pharmacologically active compounds, composed of 1,280 in vivo-active drugs, and identified ebselen [2-phenyl-1,2-benzisoselenazol-3(2H)-one], an organoselenium compound, as an inhibitor of HIV-1 capsid CTD dimerization. Nuclear magnetic resonance (NMR) spectroscopic analysis confirmed the direct interaction of ebselen with the HIV-1 capsid CTD and dimer dissociation when ebselen is in 2-fold molar excess. Electrospray ionization mass spectrometry revealed that ebselen covalently binds the HIV-1 capsid CTD, likely via a selenylsulfide linkage with Cys198 and Cys218. This compound presents anti-HIV activity in single and multiple rounds of infection in permissive cell lines as well as in primary peripheral blood mononuclear cells. Ebselen inhibits early viral postentry events of the HIV-1 life cycle by impairing the incoming capsid uncoating process. This compound also blocks infection of other retroviruses, such as Moloney murine leukemia virus and simian immunodeficiency virus, but displays no inhibitory activity against hepatitis C and influenza viruses. This study reports the use of TR-FRET screening to successfully identify a novel capsid inhibitor, ebselen, validating HIV-1 capsid as a promising target for drug development.

Non-Metal and Enzymatic Catalysts for Hydroperoxide Oxidation of Organic Compounds

Oxidation of different groups of organic compounds, with hydroperoxides catalyzed by non-heavy metal containing low-molecular-weight compounds and enzymes is reviewed. This article is concentrated mainly on the hydrogen peroxide and tert-butyl hydroperoxide, however other less common hydroperoxides are also mentioned. Since hydroperoxides themselves are inactive toward most of the organic substrates, in situ activation of the oxidant is necessary. For this purpose various activators have been applied in stoichiometric or catalytic amounts. The carboxylic acids, nitriles, amides and urea are representative for the first category. The organocatalysts such as � -halo carbonyl compounds, ketones, imines, iminium salts, nitroxyl radicals and polyaminoacids, selenium compounds and enzymes are presented. They are involved in oxygen, and electron transfer processes whose mechanisms are briefly discussed, and their applications in laboratory and industrial synthesis are indicated.

Selected ebselen analogs reduce mechlorethamine toxicity in vitro.

Abstract Sulfur mustard (SM) is a potent vesicant. The lack of an effective antidote makes SM a continued threat to both military and civilian settings. A surrogate agent, namely mechlorethamine (HN2), was used here to mimic the toxicity of SM, and the main objective of this study was to demonstrate if selected organoselenium analogs could protect cultured A-431 skin cells from HN2 toxicity. Test compounds included ebselen (EB-1) and three related organoselenium analogs (EB-2, EB-3 and EB-4). In the absence of test compound, a reproducible and robust cell death was observed in the cells following incubation with HN2 (25u2009µM, 24 or 48u2009h) while cells treated with test compound alone (15, 30 or 60u2009µM) for similar periods of time were generally not affected. When incubated in the presence of both HN2 and test compound for 24 or 48u2009h, it was found that EB-1, EB-2, EB-3 and EB-4 could spare the cells from death, with the EB-4 compound being the most effective at reducing HN2 toxicity. Light microscopy confirmed these findings. The organoseleniums were also examined for their effects on reducing lipid peroxidation in the A-431 skin cells. Among the test compounds, EB-4 reduced lipid peroxidation by HN2 to the greatest extent. These studies, taken together, validate that the organoselenium antioxidants tested here may serve a purpose in the discovery of medical countermeasures to vesicants.

Ebselen Analogues Reduce 2-chloroethyl Ethyl Sulphide Toxicity in A-431 Cells

Vesicants are potent blistering agents. The prototype vesicant is sulphur mustard gas, first used in World War I, which still has no effective antidote. We used a mustard gas surrogate 2-chloroethyl ethyl sulphide (CEES) to study the ability of resveratrol (RES) and pterostilbene (PTS), two well-established stilbene antioxidants, ebselen (EB-1), an organoselenium compound, and three EB-1 analogues (EB-2, EB-3, and EB-4) to reduce CEES toxicity in human epidermoid carcinoma cells (A-431). Following a 24-hour incubation of a toxic concentration of CEES (1000 μmol L-1), we used the MTT [3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide] test to analyse cell viability. Different concentrations of test antioxidants alone (15 μmol L-1, 30 μmol L-1 or 60 μmol L-1) did not decrease cell viability. Treatment with CEES and test antioxidants for 24 h showed that only EB-1 and its analogues EB-2, EB-3, and EB-4 but not the stilbene compounds could rescue the cells from death. EB-1 and EB-4 were the most effective at reducing CEES cytotoxicity and did so in a concentration-dependent manner, while EB-2 and EB-3 demonstrated the least protective effect. In summary, the data described herein indicate that organoselenium antioxidants, especially EB-4, may prove useful as countermeasures to blistering agents.

Reaction of bis[(2-chlorocarbonyl)phenyl] Diselenide with Phenols, Aminophenols, and Other Amines towards Diphenyl Diselenides with Antimicrobial and Antiviral Properties

A reaction of bis[(2-chlorocarbonyl)phenyl] diselenide with various mono and bisnucleophiles such as aminophenols, phenols, and amines have been studied as a convenient general route to a series of new antimicrobial and antiviral diphenyl diselenides. The compounds, particularly bis[2-(hydroxyphenylcarbamoyl)]phenyl diselenides and reference benzisoselenazol-3(2H)-ones, exhibited high antimicrobial activity against Gram-positive bacterial species (Enterococcus spp., Staphylococcus spp.), and some compounds were also active against Gram-negative E. coli and fungi (Candida spp., A. niger). The majority of compounds demonstrated high activity against human herpes virus type 1 (HHV-1) and moderate activity against encephalomyocarditis virus (EMCV), while they were generally inactive against vesicular stomatitis virus (VSV).

Ebselen Reduces the Toxicity of Mechlorethamine in A-431 Cells via Inhibition of Apoptosis

A series of test compounds were evaluated for an ability to reduce the toxicity of the nitrogen mustard mechlorethamine (HN2) in vitro. The test compounds included resveratrol, pterostilbene, vitamin C, ebselen, ebselen diselenide, and ebselen‐sulfur. Among them, ebselen demonstrated the highest degree of protection against HN2 toxicity. To this end, pretreatment of the cells with ebselen offered protection against the toxicant whereas no protection was observed when cells were first incubated with HN2 and then treated with ebselen. Significant increases in caspase 3 and caspase 9 activities were observed in response to HN2, and ebselen was found to reduce these effects. Taken together, the data presented here indicate that ebselen is an effective countermeasure to nitrogen mustard in vitro, which is worthy of future investigation in vivo.

In vitro assessment of the growth and plasma membrane H+-ATPase inhibitory activity of ebselen and structurally related selenium- and sulfur-containing compounds in Candida albicans

Ebselen (EB, compound 1) is an investigational organoselenium compound that reduces fungal growth, in part, through inhibition of the fungal plasma membrane H+‐ATPase (Pma1p). In the present study, the growth inhibitory activity of EB and of five structural analogs was assessed in a fluconazole (FLU)‐resistant strain of Candida albicans (S2). While none of the compounds were more effective than EB at inhibiting fungal growth (IC50 ∼ 18 μM), two compounds, compounds 5 and 6, were similar in potency. Medium acidification assays performed with S2 yeast cells revealed that compounds 4 and 6, but not compounds 2, 3, or 5, exerted an inhibitory activity comparable to EB (IC50 ∼ 14 μM). Using a partially purified Pma1p preparation obtained from S2 yeast cells, EB and all the analogs demonstrated a similar inhibitory activity. Taken together, these results indicate that EB analogs are worth exploring further for use as growth inhibitors of FLU‐resistant fungi.