Evaluating 5-nitrofurans as trypanocidal agents

The nitroheterocycle nifurtimox, as part of a nifurtimox-eflornithine combination therapy, represents one of a limited number of treatments targeting Trypanosoma brucei, the causative agent of human African trypanosomiasis. The mode of action of this prodrug involves an initial activation reaction catalysed by a type I nitroreductase (NTR), an enzyme found predominantly in prokaryotes, leading to the formation of a cytotoxic unsaturated open chain nitrile metabolite. Here, we evaluate the trypanocidal activity of a library of other 5-nitrofurans against bloodstream form T. brucei as a preliminary step in the identification of additional nitroaromatic compounds that could potentially partner eflornithine. Biochemical screening against purified enzyme revealed that all 5-nitrofurans were effective substrates for TbNTR with the preferred compounds having apparent kcat/KM values approximately 50-fold greater than nifurtimox. For several compounds, in vitro reduction by this nitroreductase yielded products characterized by mass spectroscopy as either unsaturated or saturated open chain nitriles. When tested against bloodstream form T. brucei, many of the derivatives displayed significant growth inhibitory properties with the most potent compounds generating IC50 values around 200 nM. The anti-parasitic activity of the most potent agents was demonstrated to be NTR dependent as parasites having reduced levels of the enzyme displayed resistance to the compounds while parasites over expressing TbNTR showed hypersensitivity. We conclude that other members of the 5-nitrofurans class of nitroheterocycles have potential to treat human African trypanosomiasis perhaps as an alternative partner prodrug to nifurtimox in the next generation of eflornithine-based combinational therapies

Nano-Aptamer for Breast Cancer Imaging: Initial Considerations.

The application of aptamers especially in the use of drug delivery systems (DDSs) has the potential to develop in vivo nanoparticles for theranosis (therapy+diagnosis). With the advent of medical imaging and radiotherapeutics, this area of research developing the next era of radiopharmaceuticals is both attractive and promising. Overall, nano-radiopharmaceuticals have the potential to solve several problems regarding the in vivo stability of aptamers. This paper discusses a study in the development and proof-of-concept of nano-aptamers and supporting its use as a nano-radiopharmaceutical for the treatment of breast cancer and other potentially related disease states

Development, validation and application of a GC-MS method for the simultaneous detection and quantification of neutral lipid species in Trypanosoma cruzi

The development and validation of an analytical method for the simultaneous analysis of five neutral lipids in Trypanosoma cruzi epimastigotes by GC-MS is presented in this study. The validated method meets all validation parameters for all components and the chromatographic conditions have been optimized during its development. This analytical method has demonstrated good selectivity, accuracy, within-day precision, recovery and linearity in each of the established ranges. In addition, detection and quantification limits for squalene, cholesterol, ergosterol and lanosterol have been improved and it is worth highlighting the fact that this is the first time that squalene-2,3-epoxide validation data have been reported. The new validated method has been applied to epimastigotes treated with compounds with in vitro anti- T.cruzi activity. This new methodology is straightforward and constitutes a tool for screening possible sterol biosynthesis pathway inhibitors in Trypanosoma cruzi, one of the most studied targets in Chagas disease treatment. Therefore, it is an interesting and useful contribution to medicinal chemistry research

Phenazine N,N′-dioxide scaffold as selective hypoxic cytotoxin pharmacophore. Structural modifications looking for further DNA topoisomerase II-inhibition activity

Phenazine-5,10-dioxides have been identified as prodrugs for antitumour therapy that undergo hypoxic-selective bioreduction, in the solid tumour cells, to form cytotoxic species. We investigated structural modifications of the phenazine-5,10-dioxide scaffold attempting to find new selective hypoxic cytotoxins with additional ability to inhibit DNA topoisomerase II. Four series of new phenazine-5,10-dioxides aryl-substituted connected by different linkers were prepared. The clonogenic survivals of V79 cells on aerobic and anaerobic conditions were determined, and studies of oxic DNA-interaction and hypoxic DNA topoisomerase II-inhibition, for the most relevant derivatives, were performed. Four new hypoxic-selective cytotoxins were identified at the assayed doses. In some of them were operative the DNA-interaction and/or the inhibition of DNA topoisomerase II. For one of the unselective cytotoxin biotransformation studies were performed on aerobic and anaerobic conditions, explaining the lack of selectivity

Synthesis and biological evaluation of quinoxaline di-N-oxide derivatives with in vitro trypanocidal activity

Abstract: We report the synthesis and in vitro activity against T. cruzi epimastigotes of 15 novel quinoxaline derivatives. Ten of the derivatives presented IC50 values lower than the reference drugs Nfx and Bzn; four of them standed out with IC50 values lower than 1.5 M. Moreover, unspecific cytotoxicity and genotoxicity studies are also reported. Compound 14 showed a SI higher than 24, whereas compound 10 was the only one that was negative in the genotoxicity screening

New copper-based complexes with quinoxaline 'N POT.1', 'N POT.4'-dioxide derivatives, potential antitumoral agents

Taking into account our previous studies on cytotoxic metal compounds, new copper complexes with 3-aminoquinoxaline-2-carbonitrile N1,N4-dioxide derivatives as ligands were synthesized and characterized by different spectroscopic methods. The hypoxic selective cytotoxicity towards V79 cells and the superoxide dismutase-like activity of the complexes were determined and related to physicochemical properties of the compounds. In particular, the copper(II) complex with 3-amino-6-chloro-7-fluoroquinoxaline-2-carbonitrile N1,N4-dioxide showed cytotoxic selectivity in hypoxia being the most lipophilic compound of the series. On the contrary, the complex with 3-aminoquinoxaline-2-carbonitrile N1,N4-dioxide was cytotoxic but not selective and that with 3-amino-7-chloro-6-methoxy-quinoxaline-2-carbonitrile N1,N4-dioxide was not cytotoxic towards V79 cells neither in oxia nor in hypoxia in the assayed conditions. The σm Hammett substituent electronic descriptor was related to the effect in hypoxic conditions and the SOD-like activity was correlated to the effect in normoxia.Comisión Honoraria de Lucha Contra el Cáncer (CHLCC)Comisión Sectorial de Investigación Científica (CSIC)PEDECIB

Quantitative High-Throughput Screen Identifies Inhibitors of the Schistosoma mansoni Redox Cascade

Schistosomiasis is a tropical disease associated with high morbidity and mortality, currently affecting over 200 million people worldwide. Praziquantel is the only drug used to treat the disease, and with its increased use the probability of developing drug resistance has grown significantly. The Schistosoma parasites can survive for up to decades in the human host due in part to a unique set of antioxidant enzymes that continuously degrade the reactive oxygen species produced by the host's innate immune response. Two principal components of this defense system have been recently identified in S. mansoni as thioredoxin/glutathione reductase (TGR) and peroxiredoxin (Prx) and as such these enzymes present attractive new targets for anti-schistosomiasis drug development. Inhibition of TGR/Prx activity was screened in a dual-enzyme format with reducing equivalents being transferred from NADPH to glutathione via a TGR-catalyzed reaction and then to hydrogen peroxide via a Prx-catalyzed step. A fully automated quantitative high-throughput (qHTS) experiment was performed against a collection of 71,028 compounds tested as 7- to 15-point concentration series at 5 µL reaction volume in 1536-well plate format. In order to generate a robust data set and to minimize the effect of compound autofluorescence, apparent reaction rates derived from a kinetic read were utilized instead of end-point measurements. Actives identified from the screen, along with previously untested analogues, were subjected to confirmatory experiments using the screening assay and subsequently against the individual targets in secondary assays. Several novel active series were identified which inhibited TGR at a range of potencies, with IC50s ranging from micromolar to the assay response limit (∼25 nM). This is, to our knowledge, the first report of a large-scale HTS to identify lead compounds for a helminthic disease, and provides a paradigm that can be used to jump-start development of novel therapeutics for other neglected tropical diseases

Functional foods. Reflexions of a scientist regarding a market in expansion

The International Union of Pure and Applied Chemistry (IUPAC) decidió en 2006 impulsar el estudio en América Latina de los nutracéuticos como una oportunidad científica y de interés comercial para toda la comunidad. La inciativa, impulsada por el Subcommittee on Medicinal Chemistry and Drug Development de la IUPAC, presidido por C.R. Ganellin, ha permitido unir esfuerzos de investigadores de América Latina. El proyecto se ha realizado con una presentación general del tema, que se corresponde con este trabajo, al que seguirá inmediatamente una publicación acerca de la situación concreta en diferentes países de la región. El trabajo se presenta de forma simultánea en distintas revistas de manera que se facilite el acceso a él y su siguiente discusión por parte de los interesados, en un intento de crear un clima de interés por el tema sobre la base de la investigación de conocimientos tradicionales y experiencias científicas que permitan la innovación en beneficio de todos, muy especialmente, de las sociedades productoras, así como de las personas que precisen de los compuesto

Functional foods. Reflexions of a scientist regarding a market in expansion

The International Union of Pure and Applied Chemistry (IUPAC) decidió en 2006 impulsar el estudio en América Latina de los nutracéuticos como una oportunidad científica y de interés comercial para toda la comunidad. La inciativa, impulsada por el Subcommittee on Medicinal Chemistry and Drug Development de la IUPAC, presidido por C.R. Ganellin, ha permitido unir esfuerzos de investigadores de América Latina. El proyecto se ha realizado con una presentación general del tema, que se corresponde con este trabajo, al que seguirá inmediatamente una publicación acerca de la situación concreta en diferentes países de la región. El trabajo se presenta de forma simultánea en distintas revistas de manera que se facilite el acceso a él y su siguiente discusión por parte de los interesados, en un intento de crear un clima de interés por el tema sobre la base de la investigación de conocimientos tradicionales y experiencias científicas que permitan la innovación en beneficio de todos, muy especialmente, de las sociedades productoras, así como de las personas que precisen de los compuesto

Identification of Thioredoxin Glutathione Reductase Inhibitors That Kill Cestode and Trematode Parasites

Parasitic flatworms are responsible for serious infectious diseases that affect humans as well as livestock animals in vast regions of the world. Yet, the drug armamentarium available for treatment of these infections is limited: praziquantel is the single drug currently available for 200 million people infected with Schistosoma spp. and there is justified concern about emergence of drug resistance. Thioredoxin glutathione reductase (TGR) is an essential core enzyme for redox homeostasis in flatworm parasites. In this work, we searched for flatworm TGR inhibitors testing compounds belonging to various families known to inhibit thioredoxin reductase or TGR and also additional electrophilic compounds. Several furoxans and one thiadiazole potently inhibited TGRs from both classes of parasitic flatworms: cestoda (tapeworms) and trematoda (flukes), while several benzofuroxans and a quinoxaline moderately inhibited TGRs. Remarkably, five active compounds from diverse families possessed a phenylsulfonyl group, strongly suggesting that this moiety is a new pharmacophore. The most active inhibitors were further characterized and displayed slow and nearly irreversible binding to TGR. These compounds efficiently killed Echinococcus granulosus larval worms and Fasciola hepatica newly excysted juveniles in vitro at a 20 µM concentration. Our results support the concept that the redox metabolism of flatworm parasites is precarious and particularly susceptible to destabilization, show that furoxans can be used to target both flukes and tapeworms, and identified phenylsulfonyl as a new drug-hit moiety for both classes of flatworm parasites