Synthesis and evaluation of indatraline-based inhibitors for trypanothione reductase

Exploring the synthetic potential of a marine transaminase including discrimination at a remote stereocentre

The marine transaminase, P-ω-TA, can be employed for the transamination from 1-aminotetralins and 1-aminoindanes with differentiation of stereochemistry at both the site of reaction and at a remote stereocentre resulting in formation of ketone products with up to 93% ee. While 4-substituents are tolerated on the tetralin core, the presence of 3- or 8-substituents is not tolerated by the transaminase. In general P-ω-TA shows capacity for remote diastereoselectivity, although both the stereoselectivity and efficiency are dependent on the specific substrate structure. Optimum efficiency and selectivity are seen with 4-haloaryl-1-aminotetralins and 3-haloaryl-1-aminoindanes, which may be associated with the marine origin of this enzyme.

Thiazolidinone/thiazole based hybrids - New class of antitrypanosomal agents

Different compounds have been investigated as potent drugs for trypanosomiasis treatment, but no new drug has been marketed in the past 3 decades. 4-Thiazolidinone/thiazole as privileged structures and thiosemicarbazides cyclic analogs are well known scaffolds in novel antitrypanosomal agent design. We present here the design and synthesis of new hybrid molecules bearing thiazolidinone/thiazole cores linked by the hydrazone group with various molecular fragments. Structure optimization led to compounds with phenyl-indole or phenyl-imidazo[2,1-b][1,3,4]thiadiazole moieties showing excellent antitrypanosomal activity towards Trypanosoma brucei brucei and Trypanosoma brucei gambiense. Biological study allowed identifying compounds with the submicromolar levels of IC₅₀, good selectivity indexes and relatively low cytotoxicity upon human primary fibroblasts as well as low acute toxicity.

E- and Z-, di- and tri-substituted alkenyl nitriles through catalytic cross-metathesis

Nitriles are found in many bioactive compounds, and are among the most versatile functional groups in organic chemistry. Despite many notable recent advances, however, there are no approaches that may be used for preparation of di- or trisubstituted alkenyl nitriles. Related approaches which are broad in scope and can deliver the desired products in high stereoisomeric purity are especially scarce. Here, we describe the development of several efficient catalytic cross-metathesis strategies, which provide direct access to a considerable range of Z- or E-disubstituted cyano-substituted alkenes or their corresponding trisubstituted variants. Depending on the reaction type, a molybdenum-based monoaryloxide pyrrolide (MAP) or chloride (MAC) complex may be the optimal choice. The utility of the approach, enhanced by an easy-to-apply protocol for utilization of substrates bearing an alcohol or a carboxylic acid moiety, is highlighted in the context of applications to synthesis of biologically active compounds.

Synthesis of polysubstituted 3-aminoindenes via rhodium-catalysed [3+2] cascade annulations of benzimidates with alkenes

A novel Rh-catalysed intermolecular [3+2] cascade cyclization of benzimidates and alkenes has been developed to assemble polysubstituted 3-aminoindenes, which exhibits good functional-group tolerance and excellent regioselectivity.

Molecular Basis of the Leishmanicidal Activity of the Antidepressant Sertraline as a Drug Repurposing Candidate

Drug repurposing affords the implementation of new treatments at a moderate cost and under a faster time-scale. Most of the clinical drugs against Leishmania share this origin. The antidepressant sertraline has been successfully assayed in a murine model of visceral leishmaniasis. Nevertheless, sertraline targets in Leishmania were poorly defined. In order to get a detailed insight into the leishmanicidal mechanism of sertraline on Leishmania infantum, unbiased multiplatform metabolomics and transmission electron microscopy were combined with a focused insight into the sertraline effects on the bioenergetics metabolism of the parasite. Sertraline induced respiration uncoupling, a significant decrease of intracellular ATP level, and oxidative stress in L. infantum promastigotes. Metabolomics evidenced an extended metabolic disarray caused by sertraline. This encompasses a remarkable variation of the levels of thiol-redox and polyamine biosynthetic intermediates, as well as a shortage of intracellular amino acids used as metabolic fuel by Leishmania Sertraline killed Leishmania through a multitarget mechanism of action, tackling essential metabolic pathways of the parasite. As such, sertraline is a valuable candidate for visceral leishmaniasis treatment under a drug repurposing strategy.

Synthesis, biological profiling and mechanistic studies of 4-aminoquinoline-based heterodimeric compounds with dual trypanocidal-antiplasmodial activity

Dual submicromolar trypanocidal-antiplasmodial compounds have been identified by screening and chemical synthesis of 4-aminoquinoline-based heterodimeric compounds of three different structural classes. In Trypanosoma brucei, inhibition of the enzyme trypanothione reductase seems to be involved in the potent trypanocidal activity of these heterodimers, although it is probably not the main biological target. Regarding antiplasmodial activity, the heterodimers seem to share the mode of action of the antimalarial drug chloroquine, which involves inhibition of the haem detoxification process. Interestingly, all of these heterodimers display good brain permeabilities, thereby being potentially useful for late stage human African trypanosomiasis. Future optimization of these compounds should focus mainly on decreasing cytotoxicity and acetylcholinesterase inhibitory activity.

The design and synthesis of potent and selective inhibitors of Trypanosoma brucei glycogen synthase kinase 3 for the treatment of human african trypanosomiasis

Glycogen synthase kinase 3 (GSK3) is a genetically validated drug target for human African trypanosomiasis (HAT), also called African sleeping sickness. We report the synthesis and biological evaluation of aminopyrazole derivatives as Trypanosoma brucei GSK3 short inhibitors. Low nanomolar inhibitors, which had high selectivity over the off-target human CDK2 and good selectivity over human GSK3β enzyme, have been prepared. These potent kinase inhibitors demonstrated low micromolar levels of inhibition of the Trypanosoma brucei brucei parasite grown in culture.

Probing the dimerization interface of Leishmania infantum trypanothione reductase with site-directed mutagenesis and short peptides

Binding at the interface: We tested the inhibitory activity of a set of peptide sequences derived from an α-helix of the dimeric trypanothione reductase from Leishmania infantum. Replacement of a glutamic acid residue with a lysine promoted monomer dissociation and enzyme inhibition.

Glutathione analogs in prokaryotes

BACKGROUND

Oxygen is both essential and toxic to all forms of aerobic life and the chemical versatility and reactivity of thiols play a key role in both aspects. Cysteine thiol groups have key catalytic functions in enzymes but are readily damaged by reactive oxygen species (ROS). Low-molecular-weight thiols provide protective buffers against the hazards of ROS toxicity. Glutathione is the small protective thiol in nearly all eukaryotes but in prokaryotes the situation is far more complex.

SCOPE OF REVIEW

This review provides an introduction to the diversity of low-molecular-weight thiol protective systems in bacteria. The topics covered include the limitations of cysteine as a protector, the multiple origins and distribution of glutathione biosynthesis, mycothiol biosynthesis and function in Actinobacteria, recent discoveries involving bacillithiol found in Firmicutes, new insights on the biosynthesis and distribution of ergothioneine, and the potential protective roles played by coenzyme A and other thiols.

MAJOR CONCLUSIONS

Bacteria have evolved a diverse collection of low-molecular-weight protective thiols to deal with oxygen toxicity and environmental challenges. Our understanding of how many of these thiols are produced and utilized is still at an early stage.

GENERAL SIGNIFICANCE

Extensive diversity existed among prokaryotes prior to evolution of the cyanobacteria and the development of an oxidizing atmosphere. Bacteria that managed to adapt to life under oxygen evolved, or acquired, the ability to produce a variety of small thiols for protection against the hazards of aerobic metabolism. Many pathogenic prokaryotes depend upon novel thiol protection systems that may provide targets for new antibacterial agents. This article is part of a Special Issue entitled Cellular functions of glutathione.

Redox-active antiparasitic drugs

SIGNIFICANCE

Parasitic diseases affect hundreds of millions of people worldwide and represent major health problems. Treatment is becoming extremely difficult due to the emergence of drug resistance, the absence of effective vaccines, and the spread of insecticide-resistant vectors. Thus, identification of affordable and readily available drugs against resistant parasites is of global demand.

RECENT ADVANCES

Susceptibility of many parasites to oxidative stress is a well-known phenomenon. Therefore, generation of reactive oxygen species (ROS) or inhibition of endogenous antioxidant enzymes would be a novel therapeutic approach to develop antiparasitic drugs. This article highlights the unique metabolic pathways along with redox enzymes of unicellular (Plasmodium falciparum, Trypanosoma cruzi, Trypanosoma brucei, Leishmania donovani, Entamoeba histolytica, and Trichomonas vaginalis) and multicellular parasites (Schistosoma mansoni), which could be utilized to promote ROS-mediated toxicity.

CRITICAL ISSUES

Enzymes involved in various vital redox reactions could be potential targets for drug development.

FUTURE DIRECTIONS

The identification of redox-active antiparasitic drugs along with their mode of action will help researchers around the world in designing novel drugs in the future.