Caged Dexamethasone to Photo-control the Development of Embryos through Activation of the Glucocorticoid Receptor

Efficient tools for controlling molecular functions with exquisite spatiotemporal resolution are much in demand to investigate biological processes in living systems. Here we report an easily synthesized caged dexamethasone for photo-activating cytoplasmic proteins fused to the glucocorticoid receptor. In the dark, it is stable in vitro as well as in vivo in both zebrafish (Danio rerio) and Xenopus sp, two significant models of vertebrates. In contrast, it liberates dexamethasone upon UV illumination, which has been harnessed to interfere with developmental steps in embryos of these animals. Interestingly, this new system is biologically orthogonal to the one for photo-activating proteins fused to the estrogen ERT receptor, which brings great prospect for activating two distinct proteins down to the single cell level.

On the Importance of Chemical Education

Chemical education, together with other scientific and non-scientific fields, plays a role in the construction of a rational mind, and it is therefore of the highest importance to include it as early as possible in the school curricula. In this short article, the author, not being an expert in educational sciences, expresses his personal opinion based on almost 30 years of teaching chemistry at various levels.

In Vitro and In Silico Potential Inhibitory Effects of New Biflavonoids from Ochna rhizomatosa on HIV-1 Integrase and Plasmodium falciparum

The aim of this study was to identify bioactive secondary metabolites from Ochna rhizomatosa with potential inhibitory effects against HIV and Plasmodium falciparum. A phytochemical study of O. rhizomatosa root barks resulted in the identification of three new biflavonoids (1–3), along with four known ones (4–7). Compound 7 (Gerontoisoflavone A) was a single flavonoid present in the rootbark of the plant and was used as a reference. Compound 1 (IC₅₀ = 0.047 µM) was the only one with a noteworthy inhibitory effect against HIV-1 integrase in vitro. Chicoric acid (IC₅₀ = 0.006 µM), a pure competitive inhibitor of HIV-1 integrase, was used as control. Compound 2 exhibited the highest antiplasmodial activity (IC₅₀ = 4.60 µM) against the chloroquine-sensitive strain of Plasmodium falciparum NF54. Computational molecular docking revealed that compounds 1 and 2 had the highest binding score (−121.8 and −131.88 Kcal/mol, respectively) in comparison to chicoric acid and Dolutegravir (−116 and −100 Kcal/mol, respectively), towards integrase receptor (PDB:3LPT). As far as Plasmodium-6 cysteine s48/45 domain inhibition is concerned, compounds 1 and 2 showed the highest binding scores in comparison to chloroquine, urging the analysis of these compounds in vivo for disease treatment. These results confirm the potential inhibitory effect of compounds 1 and 2 for HIV and malaria treatment. Therefore, our future investigation to find inhibitors of these receptors in vivo could be an effective strategy for developing new drugs.

Antiplasmodial activities of indole alkaloids from Tabernaemontana penduliflora K. Schum (Apocynaceae)

Five undescribed carboxy-indole alkaloids with corynanthe skeleton, penduflorines A-E (1-3) as well as a voacangine-N-oxide alkaloid, tabernaemontine (4), were isolated along with eight other known compounds (5-12) from the trunk bark of Tabernaemontana penduliflora K. Schum (Apocynaceae). Their structures were determined by means of spectroscopic and spectrometric methods such as UV, IR, NMR and HR-ESI-MS. Antiplasmodial activities of new isolates were evaluated against two strains of Plasmodium falciparum 3D7 and Dd2 by the Sybr green I-based fluorescence assay setup. Those compounds showed good in vitro activities. Among them, penduflorines A and B (1a and 1b) as well as tabernaemontine (4) showed significant inhibitory activities against the two strains with IC₅₀ values ranged between 1.85 and 7.88 μg/mL. This is the first report of quaternary-N-indole alkaloids (1a, 1b, 2, 3a, 3b and 4) occurring in the form of zwitterion from Tabernaemontana genus.

New cytotoxic obacunone-type limonoid and others constituents from the stem bark of Carapa procera DC (Meliaceae)

The phytochemical study of the CH₂Cl₂- MeOH (1:1, v/v) extract of the stem bark of Carapa procera DC (Meliaceae) led to the isolation and characterisation of a new natural limonoid 7β-obacunol (6), along with seven known compounds. Their structures were elucidated by spectroscopic means, including 1 D and 2 D NMR, HRESI-MS and by comparison with published data. The cytotoxicity of compounds 1-6 was assessed in vitro by the WST-1 assay on human lung adenocarcinoma A549 and Raw 264.7 mouse macrophage cell lines. Results suggested that obacunone (3) exhibited the most potent cytotoxic effect against A549 and Raw 264.7 cells with respective IC₅₀ values of 25.24 µM and 29.14 µM, while the new natural limonoid 7β-obacunol (6) exhibited 32.75 µM and 39.19 µM, respectively on both cell lines. Therefore, limonoid derivatives might be promising sources of natural bioactive metabolites against cancer.

Novel Aryl-Substituted Pyrimidones as Inhibitors of 3-Mercaptopyruvate Sulfurtransferase with Antiproliferative Efficacy in Colon Cancer

The enzyme 3-mercaptopyruvate sulfurtransferase (3-MST) is one of the more recently identified mammalian sources of H₂S. A recent study identified several novel 3-MST inhibitors with micromolar potency. Among those, (2-[(4-hydroxy-6-methylpyrimidin-2-yl)sulfanyl]-1-(naphthalen-1-yl)ethan-1-one) or HMPSNE was found to be the most potent and selective. We now took the central core of this compound and modified the pyrimidone and the arylketone sides independently. A 63-compound library was synthesized; compounds were tested for H₂S generation from recombinant 3-MST in vitro. Active compounds were subsequently tested to elucidate their potency and selectivity. Computer modeling studies have delineated some of the key structural features necessary for binding to the 3-MST's active site. Six novel 3-MST inhibitors were tested in cell-based assays: they exerted inhibitory effects in murine MC38 and CT26 colon cancer cell proliferation; the antiproliferative effect of the compound with the highest potency and best cell-based activity (1b) was also confirmed on the growth of MC38 tumors in mice.

Antimicrobial and cytotoxic activities of indole alkaloids and other constituents from the stem barks of Rauvolfia caffra Sond (Apocynaceae)

Twenty indole alkaloids, among which two undescribed ones named rauvolfianoids A (1) and B (2), were isolated from the stem barks of Rauvolfia caffra Sond along with eight other compounds from other biosynthetic pathways. The structures were elucidated by analysis of spectroscopic data, including 1 D and 2 D NMR; absolute configurations of 1 and 2 were determined by CD exciton chirality method. Compounds 1 and 2 were evaluated for antimicrobial and anticancer activities against three bacterial strains (Escherichia coli, Shigella sp and Salmonella sp) and CRC-related opportunistic pathogens. 1 showed moderate antibacterial activity against Salmonella sp with the MIC value of 25 μg/ml, while 2 exhibited weak selective activity against all tested pathogens. In addition, these alkaloids were characterized as weak apoptosis inducers in HCT116 human colon carcinoma cell line.

Is there a photochemical Hammond postulate?

In this work, a series of photochemical reactions were performed on isotopically labelled substrates to explore the validity of Hammond's postulate for the excited state.

Photochemical methods in metathesis reactions

Metathesis reactions are one of the most reliable and prevalent ways of creating a C-C bond in synthesis. Photochemical variants exist, and they have proven extremely useful for the construction of complex molecules, from natural products to Möbius rings. A variety of starting materials can undergo photometathesis reactions, including alkenes, alkynes, carbonyls, thiocarbonyls, and ketenes. While many of these reactions proceed with UV light and require harsh conditions, a handful of new techniques for visible-light photometathesis reactions have appeared recently. Given the current developments in visible-light photocatalysis, we believe that many more visible light photometathesis reactions await discovery. In this first review on the subject of photometathesis, we have gathered the relevant literature to give the reader an in-depth understanding of the field, and to inspire further development and synthetic application of these fascinating reactions.

A Simple Reaction for DNA Sensing and Chemical Delivery

Reactions templated by nucleic acids are currently at the heart of applications in biosensing and drug release. The number of chemical reactions selectively occurring only in the presence of the template, in aqueous solutions, and at room temperature and able to release a chemical moiety is still very limited. Here, we report the use of the p-nitrophenyl carbonate (NPC) as a new reactive moiety for DNA templated reactions releasing a colored reporter by reaction with a simple amine. The easily synthesized p-nitrophenyl carbonate was integrated in an oligonucleotide and showed a very good stability as well as a high reactivity toward amines, without the need for any supplementary reagent, quantitatively releasing the red p-nitrophenolate with a half-life of about 1 h.

The phytohormone forchlorfenuron decreases viability and proliferation of malignant mesothelioma cells in vitro and in vivo

Malignant mesothelioma (MM) is one of the most aggressive cancer types with a patient’s life expectancy of typically less than one year upon diagnosis. The urgency of finding novel therapeutic approaches to treat mesothelioma is evident. Here we tested the effect of the plant-growth regulator forchlorfenuron (FCF), an inhibitor of septin function(s) in mammalian cells, on the viability and proliferation of MM cell lines, as well as other tumor cell lines derived from lung, prostate, colon, ovary, cervix and breast. Exposure to FCF strongly inhibited proliferation of human and mouse (most efficiently epithelioid) MM cells and all other tumor cells in a concentration-dependent manner and led to cell cycle arrest and cell death. The role of septin 7 (SEPT7), a presumably essential target of FCF in MM cells was confirmed by an shRNA strategy. FCF was robustly inhibiting tumor cell growth in vitro at low micromolar (IC₅₀: ≈20-60µM) concentrations and more promisingly also in vivo. Initial experiments with FCF analogous revealed the importance of FCF’s chloride group for efficient cell growth inhibition. FCF’s rather low systemic toxicity might warrant for an extended search for other related and possibly more potent FCF analogues to target MM and putatively other septin-dependent tumors.

On the Sustainability of Photochemical Reactions

Photochemical reactions are often presented as intrinsically environmentally friendly ('green'). This may be indeed the case, but only in particular circumstances. This short essay comments on various aspects of the greenness of photochemical reactions, both in a historical (when only mercury-based hard UV light sources were available) and a current (with the recent introduction of LED technology and photoredox catalysis) perspective.

Contortamide, a new anti-colon cancer cerebroside and other constituents from Tabernaemontana contorta Stapf (Apocynaceae)

A new cerebroside, Contortamide (1) together with nine known compounds spegatrine (2), affinisine (3), Nb-methylaffinisine (4), ursolic acid (5), α-amyrin (6), bauerenol acetate (7), lupeol (8), betulinic acid (9) and β-sitosterolglycoside (10) were isolated from the trunk bark of Tabernaemontana contorta Stapf. The new compound 1 showed significant activity against Caco-2 colon cancer cells with the MTT method. Compounds 1-4 and 6-9 were isolated for the first time from this species.

Photochemical Amplifier Based on Self-Immolative Dendritic Spacers

A self-immolative dendritic structure was synthesized. It is based on phenol derivatives with three hydroxymethyl arms at both ortho and para positions of the core unit, potentially releasing up to 27 leaving groups in a third-generation dendrimer. The triggering event is the photolysis of a photosentive ortho-nitrobenzyl group. In doing so, we expected to transform a weak chemical or photochemical input into a large chemical output, which fulfills the definition of a molecular amplifier. Such dendrimers could find application as an indicator, a drug-delivery vector, or a solubilizing agent. The prepared dendrimer indeed released up to 27 leaving groups upon photolysis at 360 nm.

Antitubercular evaluation of root extract and isolated phytochemicals from Lophira lanceolata against two resistant strains of Mycobacterium tuberculosis

CONTEXT

The roots of Lophira lanceolata Van Tiegh. Ex Keay (Ochnaceae) have numerous medicinal values in the Central African region. Even though the MeOH extract of the roots has shown antimycobacterial activities, the constituents responsible for this inhibitory activity remain unknown.

OBJECTIVE

Phytochemical investigation of the MeOH root extract of L. lanceolata and determination of the antimycobacterial activities of that extract and constituents against the growth of Mycobacterium tuberculosis.

MATERIALS AND METHODS

Column chromatography was used to provide bioactive phytoconstituents. Those compounds were elucidated using MS and NMR spectroscopic data. Antimycobacterial screening of the extract (4.882-5000 µg/mL in DMSO during 24 h at 37 °C) and isolated compounds (0.244-250 µg/mL in DMSO during 24 h at 37 °C) was performed by microplate alamar blue assay (MABA) against two mycobacterial strains.

RESULTS

The investigation of L. lanceolata MeOH roots extract provided of mixture of unseparated biflavonoids with a newly described one, dihydrolophirone A (1a) associated to lophirone A (1b). The bioactive compounds that effectively inhibited the growth of M. tuberculosis AC45 were found to be compounds 1 and 2. They exhibited MIC values of 31.25 and 15.75 µg/mL, respectively, and their MIC was found to be 62.5 µg/mL against resistant strain AC83.

DISCUSSION AND CONCLUSIONS

It is clearly evident from the results obtained that the mycobacterial activity of L. lanceolata could be related mainly to its steroid and flavonoid contents. Therefore, this study suggests the potential of the above-mentioned classes of compounds as promising candidate agents for developing new anti-tuberculosis drugs.

Synthesis of different glutathione–sulfur mustard adducts of verified and potential biomarkers

Recently, several adducts between the chemical agent sulfur mustard (SM) and glutathione (GSH) were observed in vitro. We report the synthesis of different observed and potential GSH–SM bioadducts as reference materials for analytical investigation.

Bis-Retinoid A2E Induces an Increase of Basic Fibroblast Growth Factor via Inhibition of Extracellular Signal-Regulated Kinases 1/2 Pathway in Retinal Pigment Epithelium Cells and Facilitates Phagocytosis

Age-related macular degeneration (ARMD) is the leading cause of vision loss in developed countries. Hallmarks of the disease are well known; indeed, this pathology is characterized by lipofuscin accumulation, is principally composed of lipid-containing residues of lysosomal digestion. The N-retinyl-N-retinylidene ethanolamine (A2E) retinoid which is thought to be a cytotoxic component for RPE is the best-characterized component of lipofuscin so far. Even if no direct correlation between A2E spatial distribution and lipofuscin fluorescence has been established in aged human RPE, modified forms or metabolites of A2E could be involved in ARMD pathology. Mitogen-activated protein kinase (MAPK) pathways have been involved in many pathologies, but not in ARMD. Therefore, we wanted to analyze the effects of A2E on MAPKs in polarized ARPE19 and isolated mouse RPE cells. We showed that long-term exposure of polarized ARPE19 cells to low A2E dose induces a strong decrease of the extracellular signal-regulated kinases' (ERK1/2) activity. In addition, we showed that A2E, via ERK1/2 decrease, induces a significant decrease of the retinal pigment epithelium-specific protein 65 kDa (RPE65) expression in ARPE19 cells and isolated mouse RPE. In the meantime, we showed that the decrease of ERK1/2 activity mediates an increase of basic fibroblast growth factor (bFGF) mRNA expression and secretion that induces an increase in phagocytosis via a paracrine effect. We suggest that the accumulation of deposits coming from outer segments (OS) could be explained by both an increase of bFGF-induced phagocytosis and by the decrease of clearance by A2E. The bFGF angiogenic protein may therefore be an attractive target to treat ARMD.

Crystal structures of a copper(II) and the isotypic nickel(II) and palladium(II) complexes of the ligand (E)-1-[(2,4,6-tri-bromo-phen-yl)diazen-yl]naphthalen-2-ol

In the copper(II) complex, bis-{(E)-1-[(2,4,6-tri-bromo-phen-yl)diazen-yl]naph-thalen-2-olato}copper(II), [Cu(C16H8Br3N2O)2], (I), the metal cation is coord-inated by two N atoms and two O atoms from two bidentate (E)-1-[(2,4,6-tri-bromo-phen-yl)diazen-yl]naphthalen-2-olate ligands, forming a slightly distorted square-planar environment. In one of the ligands, the tri-bromo-benzene ring is inclined to the naphthalene ring system by 37.4 (5)°, creating a weak intra-molecular Cu⋯Br inter-action [3.134 (2) Å], while in the other ligand, the tri-bromo-benzene ring is inclined to the naphthalene ring system by 72.1 (6)°. In the isotypic nickel(II) and palladium(II) complexes, namely bis-{(E)-1-[(2,4,6-tri-bromo-phen-yl)diazen-yl]naphthalen-2-olato}nickel(II), [Ni(C16H8Br3N2O)2], (II), and bis-{(E)-1-[(2,4,6-tri-bromo-phen-yl)diazen-yl]naphthalen-2-olato}palladium(II), [Pd(C16H8Br3N2O)2], (III), respectively, the metal atoms are located on centres of inversion, hence the metal coordination spheres have perfect square-planar geometries. The tri-bromo-benzene rings are inclined to the naphthalene ring systems by 80.79 (18)° in (II) and by 80.8 (3)° in (III). In the crystal of (I), mol-ecules are linked by C-H⋯Br hydrogen bonds, forming chains along [010]. The chains are linked by C-H⋯π inter-actions, forming sheets parallel to (011). In the crystals of (II) and (III), mol-ecules are linked by C-H⋯π inter-actions, forming slabs parallel to (10-1). For the copper(II) complex (I), a region of disordered electron density was corrected for using the SQUEEZE routine in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18]. The formula mass and unit-cell characteristics of the disordered solvent mol-ecules were not taken into account during refinement.

Arene-Alkene Cycloaddition

Cycloadditions are among the most efficient chemical processes, combining atom economy, stereospecificity, and the ability to generate molecular complexity in a single step. Aromatic rings would in principle be ideal reaction partners, as they contain, at least from the topological point of view, both olefinic and diene subunits; however, the stability of the conjugated aromatic system would be broken by cycloaddition reactions, which are therefore rarely applied, because kinetics and thermodynamics hinder the process. From that aspect, photochemical activation opens interesting perspectives, as one can selectively provide excess energy to one of the reactants but not to the product, thus preventing thermal back reaction. Indeed, aromatic rings show a rich photochemistry, ranging from isomerizations, substitutions, and additions to cycloadditions. In this review, we will focus on cycloadditions, covering literature from early observations up to the present.

Probing Mechanisms of Photochemical Reactions: How to Teach a Young Dog Old Tricks

The mechanism of photochemical reactions can be difficult to study because of the very short-lived intermediates involved. State-of-the art ultrafast spectroscopic tools can be used to probe these processes, but we will show in this account that old-fashioned techniques, such as the determination of quantum yields, the measurement of isotope effects or the use of triplet quenchers and sensitizers still can give a significant insight into the mechanism of photochemical reactions.

Crystal structure of bis-{μ-1-[(E)-(3-meth-oxy-phen-yl)diazen-yl]naphthalen-2-olato-κ(3) N (2),O:O}bis-({1-[(E)-(3-meth-oxy-phen-yl)diazen-yl]naphthalen-2-olato-κ(2) N (2),O}copper(II))

The title dinuclear Cu(II) complex, [Cu2(C17H13N2O2)4], is located on an inversion centre. The Cu(II) atoms are each five-coordinated in a distorted square-pyramidal geometry by two N atoms and two O atoms from two bidentate ligands and one bridging O atom from another ligand. In the dinuclear complex, the Cu⋯Cu separation is 3.366 (3) Å. In the crystal, complex mol-ecules are linked via weak C-H⋯O hydrogen bonds, forming a layer parallel to (-101).

Synthesis of FMRFaNV, a Photoreleasable Caged Transmitter Designed to Study Neuron-Glia Interactions in the Central Nervous System

Neuroscience studies require technologies able to deliver compounds with both scale and timing compatibility with morphological and physiological synaptic properties. In this light, two-photon flash photolysis has been extensively used to successfully apply glutamate or other neurotransmitters at the synaptic level. However, the set of commercially available caged compounds is restricted and incompatible with studies demanding high cell specificity. The gain in cell specificity is especially relevant and challenging when studying neuron-glia interactions in the central nervous system. Here we develop a system to mimic the metabotropic glutamate receptor-dependent response of astrocytes, a glial cell type, following synaptic glutamate release. For this, we expressed an exogeneous orphan Gq-coupled protein of the Mas-related-gene (Mrg) family in glial cells and generated an MrgR's agonist peptide (FMRFa) that was chemically caged with a nitroveratryl photolabile protecting group (NV). NV has an appropriate quantum yield and a high absorption maximum that makes it very adapted to experiments with very short irradiation time. This novel caged compound allowed the activation of MrgR with both single- and two-photon light sources. Indeed, MrgR activation induced calcium transients and morphological changes in astrocytes as described previously. Thus, FMRFaNV is a very promising tool to study neuron-glia interactions.

Cell-permeant and photocleavable chemical inducer of dimerization

Chemical inducers of dimerization (CIDs) have been developed to orchestrate protein dimerization and translocation. Here we present a novel photocleavable HaloTag- and SNAP-tag-reactive CID (MeNV-HaXS) with excellent selectivity and intracellular reactivity. Excitation at 360 nm cleaves the methyl-6-nitroveratryl core of MeNV-HaXS. MeNV-HaXS covalently links HaloTag- and SNAP-tag fusion proteins, and enables targeting of selected membranes and intracellular organelles. MeNV-HaXS-mediated translocation has been validated for plasma membrane, late endosomes, lysosomes, Golgi, mitochondria, and the actin cytoskeleton. Photocleavage of MeNV-HaXS liberates target proteins and provides access to optical manipulation of protein relocation with high spatiotemporal and subcellular precision. MeNV-HaXS supports kinetic studies of protein dynamics and the manipulation of subcellular enzyme activities, which is exemplified for Golgi-targeted cargo and the assessment of nuclear import kinetics.

Ethyl 5-meth-oxy-2-trifluoro-methyl-1H-indole-3-carboxyl-ate

The title compound, C₁₃H₁₂F₃NO₃, is almost planar if one excludes the F atoms of the –CF₃ group [maximum deviation for the other hetero atoms = 0.069 (1) Å], and the dihedral angle between the pyrrole and benzene ring of the indole system is 2.54 (8)°. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, forming chains propagating along the a-axis direction. These chains are linked via C—H⋯O and C—H⋯F hydrogen bonds, forming a three-dimensional network.

Towards a photochemical synthesis of peptides

The laboratory preparation of peptides, once a challenge, is now a standard operation that can be automatised. However, the need for particular protecting groups requiring relatively harsh conditions for their removal (strong acids or bases) and reactive coupling agents can be problematic in specific cases (e.g. in a cell or in a microfluidic device). In this account, we describe our efforts towards a fully photochemical approach to peptide synthesis, where both the coupling and the deprotection steps use light instead of reagents. In order to selectively promote one of the two steps at a time, monochromatic light is used.