Paleo-soraphens: chemical total syntheses and biological studies

The soraphens are natural products that exhibit a molecular structure different from what would have been expected by following its polyketidal assembly line. The most significant differences are the presence of a hemiketal instead of a trisubstituted double bond and a double bond at C9 and C10 where a saturated carbon chain was expected. We were interested in the biological activity of the soraphens with architectures as described by the polyketide synthase since we hypothesized that these modifications reflect the evolutionary optimization of the soraphens. Herein we describe four additional derivatives of the so-called paleo-soraphens and their biological profiling to provide a picture of the hypothetical evolutionary optimization of this family of natural products. The syntheses required a unified and convergent strategy and their biological profiling was performed with the aid of impedance measurements. The results of these biological experiments are consistent with the proposed evolutionary optimization of the soraphens

xCELLanalyzer: A Framework for the Analysis of Cellular Impedance Measurements for Mode of Action Discovery

Mode of action (MoA) identification of bioactive compounds is very often a challenging and time-consuming task. We used a label-free kinetic profiling method based on an impedance readout to monitor the time-dependent cellular response profiles for the interaction of bioactive natural products and other small molecules with mammalian cells. Such approaches have been rarely used so far due to the lack of data mining tools to properly capture the characteristics of the impedance curves. We developed a data analysis pipeline for the xCELLigence Real-Time Cell Analysis detection platform to process the data, assess and score their reproducibility, and provide rank-based MoA predictions for a reference set of 60 bioactive compounds. The method can reveal additional, previously unknown targets, as exemplified by the identification of tubulin-destabilizing activities of the RNA synthesis inhibitor actinomycin D and the effects on DNA replication of vioprolide A. The data analysis pipeline is based on the statistical programming language R and is available to the scientific community through a GitHub repository

Novel peptidomimetic compounds containing redox active chalcogens and quinones as potential anticancer agents.

Many types of cancer cells are associated with a disturbed intracellular redox balance and oxidative stress (OS). Among the various agents employed to modulate the intracellular redox state of cells, certain redox catalysts containing quinone and chalcogen moieties have shown considerable promise. Passerini multicomponent reaction has been developed for the synthesis of agents combining two, three or even four redox centers in one molecule in a good yield. When incubated with cancer cells these agents inhibited cell proliferation and induced apoptotic cell death. Interestingly, some of these redox active compounds exhibited quite low toxicity with normal cells. The cause was obviously OS, which was reflected by significant decrease in reduced glutathione, subsequently cell cycle arrest and induction of apoptosis

Identification of myxobacteria-derived HIV inhibitors by a high-throughput two-step infectivity assay

Abstract Background Drug-resistance and therapy failure due to drug-drug interactions are the main challenges in current treatment against Human Immunodeficiency Virus (HIV) infection. As such, there is a continuous need for the development of new and more potent anti-HIV drugs. Here we established a high-throughput screen based on the highly permissive TZM-bl cell line to identify novel HIV inhibitors. The assay allows discriminating compounds acting on early and/or late steps of the HIV replication cycle. Results The platform was used to screen a unique library of secondary metabolites derived from myxobacteria. Several hits with good anti-HIV profiles were identified. Five of the initial hits were tested for their antiviral potency. Four myxobacterial compounds, sulfangolid C, soraphen F, epothilon D and spirangien B, showed EC50 values in the nM range with SI > 15. Interestingly, we found a high amount of overlapping hits compared with a previous screen for Hepatitis C Virus (HCV) using the same library. Conclusion The unique structures and mode-of-actions of these natural compounds make myxobacteria an attractive source of chemicals for the development of broad-spectrum antivirals. Further biological and structural studies of our initial hits might help recognize smaller drug-like derivatives that in turn could be synthesized and further optimized

SAR Studies of the Leupyrrins: Design and Total Synthesis of Highly Potent Simplified Leupylogs.

Invited for the cover of this issue is the group of Dirk Menche at the University of Bonn. The image depicts the natural product leupyrrin A1 and a synthetic leupylog in balance on an IC50 weighing scale. Read the full text of the article at 10.1002/chem.202002622

The myxobacterial metabolite ratjadone A inhibits HIV infection by blocking the Rev/CRM1-mediated nuclear export pathway

Background: The nuclear export of unspliced and partially spliced HIV-1 mRNA is mediated by the recognition of a leucine-rich nuclear export signal (NES) in the HIV Rev protein by the host protein CRM1/Exportin1. This makes the CRM1-Rev complex an attractive target for the development of new antiviral drugs. Here we tested the anti-HIV efficacy of ratjadone A, a CRM1 inhibitor derived from myxobacteria. Results: Ratjadone A inhibits HIV infection in vitro in a dose-dependent manner with EC50 values at the nanomolar range. The inhibitory effect of ratjadone A occurs around 12 hours post-infection and is specific for the Rev/CRM1-mediated nuclear export pathway. By using a drug affinity responsive target stability (DARTS) assay we could demonstrate that ratjadone A interferes with the formation of the CRM1-Rev-NES complex by binding to CRM1 but not to Rev. Conclusion: Ratjadone A exhibits strong anti-HIV activity but low selectivity due to toxic effects. Although this limits its potential use as a therapeutic drug, further studies with derivatives of ratjadones might help to overcome these difficulties in the future.The research is supported by grants from the Bill and Melinda Gates Foundation, Institució Catalana de Recerca i Estudis Avancats (ICREA), the Spanish Ministry of Science and Innovation SAF2010-21336, BFU2010-20803 and FPI grant number BES-2011-04856

Identification of myxobacteria-derived HIV inhibitors by a high-throughput two-step infectivity assay

Drug-resistance and therapy failure due to drug-drug interactions are the main challenges in current treatment against Human Immunodeficiency Virus (HIV) infection. As such, there is a continuous need for the development of new and more potent anti-HIV drugs. Here we established a high-throughput screen based on the highly permissive TZM-bl cell line to identify novel HIV inhibitors. The assay allows discriminating compounds acting on early and/or late steps of the HIV replication cycle. The platform was used to screen a unique library of secondary metabolites derived from myxobacteria. Several hits with good anti-HIV profiles were identified. Five of the initial hits were tested for their antiviral potency. Four myxobacterial compounds, sulfangolid C, soraphen F, epothilon D and spirangien B, showed EC50 values in the nM range with SI > 15. Interestingly, we found a high amount of overlapping hits compared with a previous screen for Hepatitis C Virus (HCV) using the same library. The unique structures and mode-of-actions of these natural compounds make myxobacteria an attractive source of chemicals for the development of broad-spectrum antivirals. Further biological and structural studies of our initial hits might help recognize smaller drug-like derivatives that in turn could be synthesized and further optimized.The research is supported by grants from the Bill and Melinda Gates Foundation, Institució Catalana de Recerca i Estudis Avancats (ICREA), the Spanish Ministry of Science and Innovation (SAF2010-21336 and BFU2010-20803), FPI grant number BES-2011-048569

Screening and characterization of molecules that modulate the biological activity of IFNs-I.

Type I Interferons (IFNs-I) are species-specific glycoproteins which play an important role as primary defence against viral infections and that can also modulate the adaptive immune system. In some autoimmune diseases, interferons (IFNs) are over-produced. IFNs are widely used as biopharmaceuticals for a variety of cancer indications, chronic viral diseases, and for their immuno-modulatory action in patients with multiple sclerosis; therefore, increasing their therapeutic efficiency and decreasing their side effects is of high clinical value. In this sense, it is interesting to find molecules that can modulate the activity of IFNs. In order to achieve that, it was necessary to establish a simple, fast and robust assay to analyze numerous compounds simultaneously. We developed four reporter gene assays (RGAs) to identify IFN activity modulator compounds by using WISH-Mx2/EGFP, HeLa-Mx2/EGFP, A549-Mx2/EGFP, and HEp2-Mx2/EGFP reporter cell lines (RCLs). All of them present a Z' factor higher than 0.7. By using these RGAs, natural and synthetic compounds were analyzed simultaneously. A total of 442 compounds were studied by the Low Throughput Screening (LTS) assay using the four RCLs to discriminate between their inhibitory or enhancing effects on IFN activity. Some of them were characterized and 15 leads were identified. Finally, one promising candidate with enhancing effect on IFN-α/-β activity and five compounds with inhibitory effect were described

The myxobacterial metabolite ratjadone A inhibits HIV infection by blocking the Rev/CRM1-mediated nuclear export pathway

Background: The nuclear export of unspliced and partially spliced HIV-1 mRNA is mediated by the recognition of a leucine-rich nuclear export signal (NES) in the HIV Rev protein by the host protein CRM1/Exportin1. This makes the CRM1-Rev complex an attractive target for the development of new antiviral drugs. Here we tested the anti-HIV efficacy of ratjadone A, a CRM1 inhibitor derived from myxobacteria. Results: Ratjadone A inhibits HIV infection in vitro in a dose-dependent manner with EC50 values at the nanomolar range. The inhibitory effect of ratjadone A occurs around 12 hours post-infection and is specific for the Rev/CRM1-mediated nuclear export pathway. By using a drug affinity responsive target stability (DARTS) assay we could demonstrate that ratjadone A interferes with the formation of the CRM1-Rev-NES complex by binding to CRM1 but not to Rev. Conclusion: Ratjadone A exhibits strong anti-HIV activity but low selectivity due to toxic effects. Although this limits its potential use as a therapeutic drug, further studies with derivatives of ratjadones might help to overcome these difficulties in the future.The research is supported by grants from the Bill and Melinda Gates Foundation, Institució Catalana de Recerca i Estudis Avancats (ICREA), the Spanish Ministry of Science and Innovation SAF2010-21336, BFU2010-20803 and FPI grant number BES-2011-04856