From ligand to complexes: inhibition of HIV-1 Integrase by beta-diketo acid metal complexes

Recently, a class of compounds bearing a β-diketo acid moiety have emerged as the most promising lead in anti-HIV-1 IN drug discovery. It is believed that the β-diketo acid pharmacophoric motif could be involved in a functional sequestration of one or both divalent metal ions, which are critical cofactors at the enzyme catalytic site. This would subsequently block the transition state of the IN-DNA complex. In this scenario, it is of paramount importance to acquire information about the mode of action of diketo acids, which could then be useful in the design of new compounds as IN inhibitors

Crystal structures of Lymphocytic choriomeningitis virus endonuclease domain complexed with diketo-acid ligands

International audienceThe Arenaviridae family, together with the Bunyaviridae and Orthomyxoviridae families, is one of the three negative-stranded RNA viral families that encode an endonuclease in their genome. The endonuclease domain is at the N-terminus of the L protein, a multifunctional protein that includes the RNA-dependent RNA polymerase. The synthesis of mRNA in arenaviruses is a process that is primed by capped nucleotides that are 'stolen' from the cellular mRNA by the endonuclease domain in cooperation with other domains of the L protein. This molecular mechanism has been demonstrated previously for the endonuclease of the prototype Lymphocytic choriomeningitis virus (LCMV). However, the mode of action of this enzyme is not fully understood as the original structure did not contain catalytic metal ions. The pivotal role played by the cap-snatching process in the life cycle of the virus and the highly conserved nature of the endonuclease domain make it a target of choice for the development of novel antiviral therapies. Here, the binding affinities of two diketo-acid (DKA) compounds (DPBA and L-742,001) for the endonuclease domain of LCMV were evaluated using biophysical methods. X-ray structures of the LCMV endonuclease domain with catalytic ions in complex with these two compounds were determined, and their efficacies were assessed in an in vitro endonuclease-activity assay. Based on these data and computational simulation, two new DKAs were synthesized. The LCMV endonuclease domain exhibits a good affinity for these DKAs, making them a good starting point for the design of arenavirus endonuclease inhibitors. In addition to providing the first example of an X-ray structure of an arenavirus endonuclease incorporating a ligand, this study provides a proof of concept that the design of optimized inhibitors against the arenavirus endonuclease is possible

Inhibition of ?±-class cytosolic human carbonic anhydrases I II IX and XII and ?²-class fungal enzymes by carboxylic acids and their derivatives: New isoform-I selective nanomolar inhibitors

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Metal-Chelating 2‑Hydroxyphenyl Amide Pharmacophore for Inhibition of Influenza Virus Endonuclease

The influenza virus PA endonuclease is an attractive target for development of novel anti-influenza virus therapeutics. Reported PA inhibitors chelate the divalent metal ion(s) in the enzyme’s catalytic site, which is located in the Nterminal part of PA (PA-Nter). In this work, a series of 2- hydroxybenzamide-based compounds have been synthesized and biologically evaluated in order to identify the essential pharmacophoric motif, which could be involved in functional sequestration of the metal ions (probably Mg2+) in the catalytic site of PA. By using HL1, H2L2, and HL3 as model ligands with Mg2+ ions, we isolated and fully characterized a series of complexes and tested them for inhibitory activity toward PA-Nter endonuclease. H2L2 and the corresponding Mg2+ complex showed an interesting inhibition of the endonuclease activity. The crystal structures of the uncomplexed HL1 and H2L2 and of the isolated magnesium complex [Mg(L3)2(MeOH)2]·2MeOH were solved by X-ray diffraction analysis. Furthermore, the speciation models for HL1, H2L2, and HL3 with Mg2+ were obtained, and the formation constants of the complexes were measured. Preliminary docking calculations were conducted to investigate the interactions of the title compounds with essential amino acids in the PANter active site. These findings supported the “two-metal” coordination of divalent ions by a donor triad atoms chemotype as a powerful strategy to develop more potent PA endonuclease inhibitors

Exploiting the Reducing Properties of Lignin for the Development of an Effective Lignin@Cu2O Pesticide

Lignin is a natural polymer produced in huge amounts by the paper industry. Innovative applications of lignin, especially in agriculture, represent a valuable way to develop a more sustainable economy. Its antioxidant and antimicrobial properties, combined with its biodegradability, make it particularly attractive for the development of plant protection products. Copper is an element that has long been used as a pesticide in agriculture. Despite its recognized antimicrobial activity, the concerns derived from its negative environmental impact is forcing research to move toward the development of more effective and sustainable copper-based pesticides. Here a simple and sustainable way of synthesizing a new hybrid material composed of Cu2O nanocrystals embedded into lignin, named Lignin@Cu2O is presented. The formation of cuprite nanocrystals leaves the biopolymer intact, as evidenced by infrared spectroscopy, gel permeation chromatography, and Pyrolysis-GC analysis. The combined activity of lignin and cuprite make Lignin@Cu2O effective against Listeria monocytogenes and Rhizoctonia solani at low copper dosage, as evidenced by in vitro and in vivo tests conducted on tomato plants

Investigation of antibacterial activity of new classes of essential oils derivatives

Essential oils (EOs) have deserved much attention in the past decades for their antimicrobial activity, since many of them have demonstrated efficacy against food-borne pathogenic and spoilage microorganisms. Moreover, they have potential application in animal nutrition as multifunctional feed supplements, avoiding or diminishing the use of antibiotics in livestock. However, low solubility and bioavailability as well as volatility and marked aromatic note are important limitations in food and feed applications. In this study we present the synthesis, characterization and evaluation of the antibacterial activity of new thymol, carvacrol and menthol derivatives. The new compounds have been designed to overcome the limitations of the precursors, such as poor water solubility and volatility, still maintaining a good antimicrobial profile. We evaluated the activity of the synthetized compounds against pathogens causing important foodborne diseases, . i.e. . Clostridium perfringens, . Salmonella typhimurium, . Salmonella enteritidis and . Escherichia coli. The low MICs and MBCs values for some of the studied compounds, combined with water solubility and negligible cytotoxicity towards HT-29 human cells, confirmed the potential use for EOs derivatives in the food industry

Development of a Raltegravir-based Photoaffinity-Labeled Probe for Human Immunodeficiency Virus-1 Integrase Capture

Photoaffinity labeling (PAL) is one of the upcoming and powerful tools in the field of molecular recognition. It includes the determination of dynamic parameters, such as the identification and localization of the target protein and the site of drug binding. In this study, a photoaffinity-labeled probe for full-length human immunodeficiency virus-1 integrase (HIV-1 IN) capture was designed and synthesized, following the structure of the FDA-approved drug Raltegravir. This photoprobe was found to retain the HIV IN inhibitory potential in comparison with its parent molecule and demonstrates the ability to label the HIV-1 IN protein. Putative photoprobe/inhibitor binding sites near the catalytic site were then identified after protein digestion coupled to mass and molecular modeling analyses

Chelation motifs affecting metal-dependent viral enzymes: N′-acylhydrazone ligands as dual target inhibitors of HIV-1 Integrase and Reverse Transcriptase Ribonuclease H domain

Human immunodeficiency virus type 1 (HIV-1) infection, still represent a serious global health emergency. The chronic toxicity derived from the current anti-retroviral therapy limits the prolonged use of several antiretroviral agents, continuously requiring the discovery of new antiviral agents with innovative strategies of action. In particular, the development of single molecules targeting two proteins (dual inhibitors) is one of the current main goals in drug discovery. In this contest, metal-chelating molecules have been extensively explored as potential inhibitors of viral metal-dependent enzymes, resulting in some important classes of antiviral agents. Inhibition of HIV Integrase (IN) is, in this sense, paradigmatic. HIV-1 IN and Reverse Transcriptase-associated Ribonuclease H (RNase H) active sites show structural homologies, with the presence of two Mg(II) cofactors, hence it seems possible to inhibit both enzymes by means of chelating ligands with analogous structural features. Here we present a series of N′-acylhydrazone ligands with groups able to chelate the Mg(II) hard Lewis acid ions in the active sites of both the enzymes, resulting in dual inhibitors with micromolar and even nanomolar activities. The most interesting identified N′-acylhydrazone analog, compound 18, shows dual RNase H-IN inhibition and it is also able to inhibit viral replication in cell-based antiviral assays in the low micromolar range. Computational modeling studies were also conducted to explore the binding attitudes of some model ligands within the active site of both the enzymes

Inhibitory effect of 2,3,5,6-tetrafluoro-4-[4-(Aryl)-1H-1,2,3-triazol-1-yl]benzenesulfonamide derivatives on HIV reverse transcriptase associated rnase H activities

The HIV-1 ribonuclease H (RNase H) function of the reverse transcriptase (RT) enzyme catalyzes the selective hydrolysis of the RNA strand of the RNA:DNA heteroduplex replication intermediate, and represents a suitable target for drug development. A particularly attractive approach is constituted by the interference with the RNase H metal-dependent catalytic activity, which resides in the active site located at the C-terminus p66 subunit of RT. Herein, we report results of an in-house screening campaign that allowed us to identify 4-[4-(aryl)-1H-1,2,3-triazol-1-yl]benzenesulfonamides, prepared by the “click chemistry” approach, as novel potential HIV-1 RNase H inhibitors. Three compounds (9d, 10c, and 10d) demonstrated a selective inhibitory activity against the HIV-1 RNase H enzyme at micromolar concentrations. Drug-likeness, predicted by the calculation of a panel of physicochemical and ADME properties, putative binding modes for the active compounds, assessed by computational molecular docking, as well as a mechanistic hypothesis for this novel chemotype are reported

Half-sandwich arene ruthenium(II) and osmium(II) thiosemicarbazone complexes : solution behavior and antiproliferative activity

We report the synthesis, characterization and antiproliferative activity of organo-osmium(II) and organo-ruthenium(II) half-sandwich complexes [(η6-p-cym)Os(L)Cl]Cl (1 and 2) and [(η6-p-cym)Ru(L)Cl]Cl (3 and 4), where L = N-(2-hydroxy)-3-metoxybenzylidenethiosemicarbazide (L1) or N-(2,3-dihydroxybenzylidene)-3-phenylthiosemicarbazide (L2), respectively. X-ray crystallography showed that all four complexes possess half-sandwich pseudo-octahedral “three- leg piano-stool” structures, with a neutral N,S-chelating thiosemicarbazone ligand and a terminal chloride occupying three coordinative positions. In methanol, E/Z isomerization of the coordinated thiosemicarbazone ligand was observed, while in an aprotic solvent like acetone, partial dissociation of the ligand occurs, reaching complete displacement in a more coordinating solvent like DMSO. In general, the complexes exhibited good activity towards A2780 ovarian, A2780Cis cisplatin-resistant ovarian, A549 lung, HCT116 colon, and PC3 prostate cancer cells. In particular ruthenium complex 3 does not present cross-resistance with the clinical drug cisplatin in the A2780 human ovarian cancer cell line. The complexes were more active than the free thiosemicarbazone ligands, especially in A549 and HCT116 cells with po- tency improvements of up to 20-fold between the organic ligand L1 and the ruthenium complex 1