A new type of quinoxalinone derivatives affects viability, invasion, and intracellular growth of Toxoplasma gondii tachyzoites in vitro.

Quinoxalinone derivatives, identified as VAM2 compounds (7-nitroquinoxalin-2-ones), were evaluated against Toxoplasma gondii tachyzoites of the RH strain. The VAM2 compounds were previously synthesized based on the design obtained from an in silico prediction with the software TOMOCOMD-CARDD. From the ten VAM2 drugs tested, several showed a deleterious effect on tachyzoites. However, VAM2-2 showed the highest toxoplasmicidal activity generating a remarkable decrease in tachyzoite viability (in about 91 %) and a minimal alteration in the host cell. An evident inhibition of host cell invasion by tachyzoites previously treated with VAM2-2 was observed in a dose-dependent manner. In addition, remarkable alterations were observed in the pellicle parasite, such as swelling, roughness, and blebbing. Toxoplasma motility was inhibited, and subpellicular cytoskeleton integrity was altered, inducing a release of its components to the soluble fraction. VAM2-2 showed a clear and specific deleterious effect on tachyzoites viability, structural integrity, and invasive capabilities with limited effects in host cells morphology and viability. VAM2-2 minimum inhibitory concentration (MIC50) was determined as 3.3 µM ± 1.8. Effects of quinoxalinone derivatives on T. gondii provide the basis for a future therapeutical alternative in the treatment of toxoplasmosis.

Antiprotozoan lead discovery by aligning dry and wet screening: prediction, synthesis, and biological assay of novel quinoxalinones.

Protozoan parasites have been one of the most significant public health problems for centuries and several human infections caused by them have massive global impact. Most of the current drugs used to treat these illnesses have been used for decades and have many limitations such as the emergence of drug resistance, severe side-effects, low-to-medium drug efficacy, administration routes, cost, etc. These drugs have been largely neglected as models for drug development because they are majorly used in countries with limited resources and as a consequence with scarce marketing possibilities. Nowadays, there is a pressing need to identify and develop new drug-based antiprotozoan therapies. In an effort to overcome this problem, the main purpose of this study is to develop a QSARs-based ensemble classifier for antiprotozoan drug-like entities from a heterogeneous compounds collection. Here, we use some of the TOMOCOMD-CARDD molecular descriptors and linear discriminant analysis (LDA) to derive individual linear classification functions in order to discriminate between antiprotozoan and non-antiprotozoan compounds as a way to enable the computational screening of virtual combinatorial datasets and/or drugs already approved. Firstly, we construct a wide-spectrum benchmark database comprising of 680 organic chemicals with great structural variability (254 of them antiprotozoan agents and 426 to drugs having other clinical uses). This series of compounds was processed by a k-means cluster analysis in order to design training and predicting sets. In total, seven discriminant functions were obtained, by using the whole set of atom-based linear indices. All the LDA-based QSAR models show accuracies above 85% in the training set and values of Matthews correlation coefficients (C) vary from 0.70 to 0.86. The external validation set shows rather-good global classifications of around 80% (92.05% for best equation). Later, we developed a multi-agent QSAR classification system, in which the individual QSAR outputs are the inputs of the aforementioned fusion approach. Finally, the fusion model was used for the identification of a novel generation of lead-like antiprotozoan compounds by using ligand-based virtual screening of 'available' small molecules (with synthetic feasibility) in our 'in-house' library. A new molecular subsystem (quinoxalinones) was then theoretically selected as a promising lead series, and its derivatives subsequently synthesized, structurally characterized, and experimentally assayed by using in vitro screening that took into consideration a battery of five parasite-based assays. The chemicals 11(12) and 16 are the most active (hits) against apicomplexa (sporozoa) and mastigophora (flagellata) subphylum parasites, respectively. Both compounds depicted good activity in every protozoan in vitro panel and they did not show unspecific cytotoxicity on the host cells. The described technical framework seems to be a promising QSAR-classifier tool for the molecular discovery and development of novel classes of broad-antiprotozoan-spectrum drugs, which may meet the dual challenges posed by drug-resistant parasites and the rapid progression of protozoan illnesses.

Synthesis and evaluation of 1,1'-hydrocarbylenebis(indazol-3-ols) as potential antimalarial drugs.

Bis(indazol-3-ol) derivatives (5, 30-38) were prepared by alkylation of 3-alkoxyindazoles with alpha,omega-dibromides, followed by removal of the O-protecting groups. These compounds were subsequently evaluated as inhibitors of biocrystallization of ferriprotoporphyrin IX (heme) to hemozoin, a Plasmodium detoxification specific process. Most bis(5-nitroindazol-3-ols) were good inhibitors, however, a denitro analogue (38), the intermediate bis(3-alkoxyindazoles) (15-29) as well as bis(indazolin-3-ones) (39-42) were not active, showing the importance of the NO(2) and OH groups in the inhibition process.

Nueva matriz orgánica con menor contracción de polimerización / New organic matrix with less polymerization shrinkage

Se modificó la matriz orgánica de composites dentales a partir de la síntesis de nuevos monómeros. Estos fueron caracterizados por espectroscopía infrarroja y resonancia magnética nuclear y se determinó su densidad y viscosidad. Además, se evaluó la contracción de polimerización total alcanzada por dichos monómeros puros y por mezclas de éstos con cantidades crecientes de Bis-GMA. La caracterización espectroscópica de los monómeros sintetizados corroboró la introducción de las modificaciones propuestas. La viscosidad de estos compuestos fue significativamente menor que la del Bis-GMA. Matrices orgánicas con los monómeros derivados presentaron menor contracción que la de las mismas proporciones de Bis-GMA y TEGDMA. De lo anterior se concluye que: a) la acilación del Bis-GMA permite obtener nuevos monómeros de menor viscosidad, ya que se elimina la posibilidad de formar uniones hidrógeno intermoleculares. b) las matrices orgánicas donde se reemplaza el TEGDMA por los monómeros sintetizados, Ac-Bis-GMA y Bz-Bis-GMA, generan menor contracción de polimerización que las originales. Realizado dentro del proyecto O022 de la Universidad de Buenos Aires, Argentina (AU)

Nueva matriz orgánica con menor contracción de polimerización / New organic matrix with less polymerization shrinkage

Se modificó la matriz orgánica de composites dentales a partir de la síntesis de nuevos monómeros. Estos fueron caracterizados por espectroscopía infrarroja y resonancia magnética nuclear y se determinó su densidad y viscosidad. Además, se evaluó la contracción de polimerización total alcanzada por dichos monómeros puros y por mezclas de éstos con cantidades crecientes de Bis-GMA. La caracterización espectroscópica de los monómeros sintetizados corroboró la introducción de las modificaciones propuestas. La viscosidad de estos compuestos fue significativamente menor que la del Bis-GMA. Matrices orgánicas con los monómeros derivados presentaron menor contracción que la de las mismas proporciones de Bis-GMA y TEGDMA. De lo anterior se concluye que: a) la acilación del Bis-GMA permite obtener nuevos monómeros de menor viscosidad, ya que se elimina la posibilidad de formar uniones hidrógeno intermoleculares. b) las matrices orgánicas donde se reemplaza el TEGDMA por los monómeros sintetizados, Ac-Bis-GMA y Bz-Bis-GMA, generan menor contracción de polimerización que las originales. Realizado dentro del proyecto O022 de la Universidad de Buenos Aires, Argentina

Synthesis and nematocide activity of S-glycopyranosyl-6,7-diarylthiolumazines.

6,7-Diaryl derivatives of mono and di-S-glycopyranosylthiolumazine derivatives 5-8 were prepared to test their nematocide activity. In vitro tests against Caenorhabditis elegans were performed and it was found that monosubstituted derivatives 5-7 showed higher activity than the corresponding unsubstituted 2-thiolumazines 1-3, whilst 2-S,4-S-di-glycopyranosylpteridine derivative 8 was inactive in contrast to unsubstituted derivative 4. In order to check whether the lack of activity of 8 was due to the two bulky substituents of the pteridine nucleus, 2-S,4-S-dimethyl derivative 9 was synthesized and assayed showing also lack of activity. A theoretical study on the stability of the different possible tautomers of compound 4 was carried out in an attempt to explain some, in appearance, anomalous (13)C NMR data of this compound.

Inhibitory effect of thiosemicarbazone derivatives on Junin virus replication in vitro.

The inhibitory effect of several thiosemicarbazones (TSCs), synthesized from aromatic ketones and terpenones, and their heterocyclic thiadiazoline (TDZ) derivatives, was investigated against Junin virus (JUNV), an arenavirus agent of Argentine haemorrhagic fever. From the 25 compounds tested, six compounds belonging to the TSC group were found to be selective inhibitors of JUNV, with EC50 values determined by a virus yield inhibition assay in the range 3.4-12.5 microM, and selectivity indices greater than 10. By contrast, most of the TDZs obtained by heterocyclization of the TSCs were not active against JUNV. No conclusive structure-activity relationships could be established but systematically higher activity was associated to TSCs derived from aromatic ketones. The mode of action of one of the most active compound, the 3,4-dihydronaphtalen-1(2H)one thiosemicarbazone (tetralone thiosemicarbazone), was studied further. This TSC lacked virucidal effects on JUNV virions. Results from time of addition experiments and viral protein expression assays suggest that tetralone thiosemicarbazone inhibited a late stage in the replicative cycle of JUNV.

Heterocyclization of 3-deoxy-D-erythro-hexos-2-ulose-1,2-bis(thiosemicarbazone). Crystal structure of the major diastereomer.

Both thiosemicarbazone groups of the derivative 1 of 3-deoxy-D-erythro-hexos-2-ulose underwent, on acetylation, a heterocyclization process to give (5R,5'R)-2,2'-diacetamido-4,4'-di-N-acetyl-5'-(1-deoxy-2,3,4-tri-O-acetyl-D-erythritol-1-yl)-5,5'-bis(1,3,4-thiadiazoline) (2) as a major product. The X-ray diffraction data of a single crystal of 2 indicated the R,R configuration for the stereocenters of the thiadiazoline rings (C-5 and C-5'). In the solid state, 2 adopts a sickle conformation (by clockwise rotation of the C-2-C-3 axis of the sugar chain) which has a S//O 1,3-parallel interaction. In solution, as determined by (1)H NMR spectroscopy which included NOE experiments, a similar sickle conformation was observed. From the reaction mixture of acetylation of 1 was isolated the bis(thiadiazoline) 3 as a by-product. The configuration of the C-5 and C-5' stereocenters of 3 were respectively assigned as S,R by comparison of the physical and spectroscopic data of this compound with those of 2.