Synthesis and anti-HIV evaluation of water-soluble calixarene-based bithiazolyl podands

Identification of Potential Drug Targets of Calix[4]arene by Reverse Docking

Calixarenes are displaying great potential for the development of new drug delivery systems, diagnostic imaging, biosensing devices and inhibitors of biological processes. In particular, calixarene derivatives are able to interact with many different enzymes and function as inhibitors. By screening of the potential drug target database (PDTD) with a reverse docking procedure, we identify and discuss a selection of 100 proteins that interact strongly with calix[4]arene. We also discover that leucine (23.5 %), isoleucine (11.3 %), phenylalanines (11.3 %) and valine (9.5 %) are the most frequent binding residues followed by hydrophobic cysteines and methionines and aromatic histidines, tyrosines and tryptophanes. Top binders are peroxisome proliferator-activated receptors that already are targeted by commercial drugs, demonstrating the practical interest in calix[4]arene. Nuclear receptors, potassium channel, several carrier proteins, a variety of cancer-related proteins and viral proteins are prominent in the list. It is concluded that calix[4]arene, which is characterized by facile access, well-defined conformational characteristics, and ease of functionalization at both the lower and higher rims, could be a potential lead compound for the development of enzyme inhibitors and theranostic platforms.

Novel xylenyl-spaced bis-thiazoles/thiazines: synthesis, biological profile as herpes simplex virus type 1 inhibitors and in silico simulations

Aims: Development of some potent bis-thiazole and bis-thiazine derivatives that could be used as antiviral prototypes. Materials & methods: Xylenyl-spaced bis-carbazone scaffold 3 was used as a versatile building block for bis-thiazole derivatives 6a-e and 9a-d and bis-thiazine derivatives 12a-f. These bis-heterocycles were screened as herpes simplex virus type 1 (HSV-1) inhibitors. Results: The new bis-heterocyclic compounds showed remarkable antiviral activity (e.g., compound 6d cytotoxicity concentration CC50 >500 μg/ml). The antiviral capacity of the synthesized bis-compounds was supported by a molecular docking study against the glycoprotein D receptor of HSV-1. Compounds 6b, 9b, and 12c displayed the best binding coefficients. Conclusion: A new series of xylenyl-spaced bis-carbazone scaffolds were used as a building scaffold to construct a host of bis-thiazole/thiazine derivatives that could be used as antiviral prototypes.

Functionalized Calixarenes as Promising Antibacterial Drugs to Face Antimicrobial Resistance

Since the discovery of polyphenolic resins 150 years ago, the study of polymeric compounds named calix[n]arene has continued to progress, and those skilled in the art perfectly know now how to modulate this phenolic ring. Consequently, calix[n]arenes are now used in a large range of applications and notably in therapeutic fields. In particular, the calix[4]arene exhibits multiple possibilities for regioselective polyfunctionalization on both of its rims and offers researchers the possibility of precisely tuning the geometry of their structures. Thus, in the crucial research of new antibacterial active ingredients, the design of calixarenes finds its place perfectly. This review provides an overview of the work carried out in this aim towards the development of intrinsically active prodrogues or metallic calixarene complexes. Out of all the work of the community, there are some excellent activities emerging that could potentially place these original structures in a very good position for the development of new active ingredients.

Photophysical and NMR studies of encapsulation of 2-cyano-6-hydroxy benzothiazole in p-sulfonatocalix[6]arene and its biological applications

This work deals with the study of the interaction between 2-cyano-6-hydroxy benzothiazole (CHBT) and p-sulfonatocalix[6]arene (SCX6) at different pH values in aqueous medium by UV-visible absorption spectroscopy and steady-state fluorescence spectroscopy. The results demonstrate the strong influence of SCX6 on the fluorescence properties of CHBT. The steady-state emission of CHBT shows strong sensitivity to its environment. The mode of inclusion complexation of CHBT and SCX6 has also been investigated using HR-MS, FT-IR, NMR, 2D NMR, and FESEM analysis. With the increase in SCX6 concentration, absorbance decreased with an isosbestic point at 305 nm. The binding constant is calculated by a spectrofluorimetric method and stoichiometry by Job's method. The formation of an inclusion complex has been confirmed by 2D NMR NOESY, COSY, ROESY, HMBC, and HSQC spectroscopic methods. The complex is seen to be stabilized by electrostatic interactions between CHBT and the nanocavity of SCX6. Studies with cellular systems support that the CHBT-SCX6 complex is more effective in killing cancerous cells and hence, SCX6 may prove to be an effective carrier for drug molecules like CHBT.

Antimicrobial Activity of Calixarenes and Related Macrocycles

Calixarenes and related macrocycles have been shown to have antimicrobial effects since the 1950s. This review highlights the antimicrobial properties of almost 200 calixarenes, resorcinarenes, and pillararenes acting as prodrugs, drug delivery agents, and inhibitors of biofilm formation. A particularly important development in recent years has been the use of macrocycles with substituents terminating in sugars as biofilm inhibitors through their interactions with lectins. Although many examples exist where calixarenes encapsulate, or incorporate, antimicrobial drugs, one of the main factors to emerge is the ability of functionalized macrocycles to engage in multivalent interactions with proteins, and thus inhibit cellular aggregation.

Synthesis of novel calix[4]arene p-benzazole derivatives and investigation of their DNA binding and cleavage activities with molecular docking and experimental studies

In this study, novel p-benzimidazole-derived calix[4]arene compounds with different structures, and a benzothiazole-derived calix[4]arene compound, were synthesized by a microwave-assisted method and their structures were determined by FTIR, 1H NMR, 13C NMR, MALDI-TOF mass spectroscopy, and elemental analysis. The effects of functional calixarenes against bacterial (pBR322 plasmid DNA) and eukaryotic DNA (calf thymus DNA = CT-DNA) were investigated. The studies with plasmid DNA have shown that compounds 6 and 10 containing methyl and benzyl groups, respectively, have DNA cleavage activity at the highest concentrations (10 000 μM). Interactions with plasmid DNA using some restriction enzymes (BamHI and HindIII) were also investigated. The binding ability of p-substituted calix[4]arene compounds towards CT-DNA was examined using UV-vis and fluorescence spectroscopy and it was determined that some compounds showed efficiency. In particular, it was observed that the functional compounds (10 and 5) containing benzyl and chloro-groups had higher activity (K b binding constants were found to be 7.1 × 103 M-1 and 9.3 × 102 M-1 respectively) on DNA than other compounds. Competitive binding experiments using ethidium bromide also gave an idea about the binding properties. Docking studies of the synthesized compounds with DNA were performed to predict the binding modes, affinities and noncovalent interactions stabilizing the DNA-compound complexes at the molecular level. Docking results were in good agreement with the experimental findings on the DNA binding activities of compounds. Based on these results, this preliminary study could shed light on future experimental antibacterial and/or anticancer research.

Heteroaromatic Polyamides with Improved Thermal and Mechanical Properties

We prepared high-performance aromatic copolyamides, containing bithiazole and thiazolo-thiazole groups in their main chain, from aromatic diamines and isophthaloyl chloride, to further improve the prominent thermal behavior and exceptional mechanical properties of commercial aramid fibers. The introduction of these groups leads to aramids with improved strength and moduli compared to commercial meta-oriented aromatic polyamides, together with an increase of their thermal performance. Moreover, their solubility, water uptake, and optical properties were evaluated in this work.

(Thia)calixarenephosphonic Acids as Potent Inhibitors of the Nucleic Acid Chaperone Activity of the HIV-1 Nucleocapsid Protein with a New Binding Mode and Multitarget Antiviral Activity

The nucleocapsid protein (NC) is a highly conserved protein that plays key roles in HIV-1 replication through its nucleic acid chaperone properties mediated by its two zinc fingers and basic residues. NC is a promising target for antiviral therapy, particularly to control viral strains resistant to currently available drugs. Since calixarenes with antiviral properties have been described, we explored the ability of calixarene hydroxymethylphosphonic or sulfonic acids to inhibit NC chaperone properties and exhibit antiviral activity. By using fluorescence-based assays, we selected four calixarenes inhibiting NC chaperone activity with submicromolar IC₅₀ values. These compounds were further shown by mass spectrometry, isothermal titration calorimetry, and fluorescence anisotropy to bind NC with no zinc ejection and to compete with nucleic acids for the binding to NC. Molecular dynamic simulations further indicated that these compounds interact via their phosphonate or sulfonate groups with the basic surface of NC but not with the hydrophobic plateau at the top of the folded fingers. Cellular studies showed that the most soluble compound CIP201 inhibited the infectivity of wild-type and drug-resistant HIV-1 strains at low micromolar concentrations, primarily targeting the early steps of HIV-1 replication. Moreover, CIP201 was also found to inhibit the flipping and polymerization activity of reverse transcriptase. Calixarenes thus form a class of noncovalent NC inhibitors, endowed with a new binding mode and multitarget antiviral activity.

Click inspired synthesis of p-tert-butyl calix[4]arene tethered benzotriazolyl dendrimers and their evaluation as anti-bacterial and anti-biofilm agents

CuAAC inspired calix-[4]arene tethered benzotriazolyl dendrimers were developed and investigated for their therapeutic potential, where 7 displayed potent anti-bacterial and anti-biofilm activities against drug-resistant & slime producing organisms.

Structural Design, Synthesis, and Preliminary Biological Evaluation of Novel Dihomooxacalix[4]arene-Based Anti-tumor Agents

Calixarene and its derivatives have extensively served as promising anti-tumor agents. Previously, we have synthesized a series of calix[n]arene polyhydroxyamine derivatives (n = 4, 6, 8) and found that 5,11,17,23-tetra-tert-butyl-25,27-bis [N-(2-hydroxyethyl)aminocarbonylmethoxyl] calix[4]arene (CLX-4) displayed significant effect toward SKOV3, A549, SW1990, HeLa, Raji, and MDA-MB-231 cancer cells. In the present work, we find a replacement of calix[4]arene bone and synthesized 19 novel structurally related dihomooxacalix[4]arene amide derivatives 4A-4S to optimize its efficacy. Their abilities to induce cytotoxicity in human lung carcinoma (A549) cells, breast cancer (MCF-7) cells, cervical cancer (HeLa) cells, hepatocellular carcinoma (HepG2) cells, as well as human umbilical vein endothelial (HUVEC) cells are evaluated in vitro. Encouraging results show that the majority of dihomooxacalix[4]arene amide derivatives are effective at inhibiting A549 cell proliferation with the corresponding IC₅₀ ranging from 0.6 to 20.1 μM. In particular, compounds 4A, 4D, and 4L explore markedly increased potency (IC₅₀ value is 2.0 ± 0.5 μM, 0.7 ± 0.1 μM, and 1.7 ± 0.4 μM) over the cytotoxicity profiles of control CLX-4, whose IC₅₀ value is 2.8 ± 0.3 μM. More interestingly, 4A also demonstrates the perfect cytotoxic effect against MCF-7, HeLa, and HepG2 cells with IC₅₀ values of 1.0 ± 0.1 μM, 0.8 ± 0.2 μM, and 2.7 ± 0.4 μM. In addition, the results proved that our synthesized 4A has much lower toxicity (41%) to normal cells at a concentration of 10 μM than that of 4D (90%). To reveal the mechanisms, the key indicators including the cell cycle and apoptosis are observed by the flow cytometry analysis in MCF-7 cells. The results demonstrate that both 4A and 4D can induce the MCF-7 cell cycle arrest in G0/G1 phase and cell apoptosis. Therefore, our finding proves that the dihomooxacalix[4]arene amide derivatives are convenient platforms for potential supramolecular anticancer agents.

Synthesis of 5,5'-Diarylimino Quinoidal 2,2'-Bithiazoles

A Pd(0)-catalyzed double C-N coupling of 5,5'-dibromo-2,2'-bithiazoles with (het)arylamines and subsequent in situ Ag₂O-mediated oxidation provides access to cross-conjugated quinoidal 5,5'-diarylimino-2,2'-bithiazoles in moderate to high yield. The highly colored quinoidal 2,2'-bithiazoles were studied by UV/vis spectroscopy, cyclic voltammetry and computational methods.

Sulfonyl-bridged Calix[4]arene as an Inhibitor of Protein Tyrosine Phosphatases

Previously, phosphonic acid derivatives of calix[4]arene and thiacalix[4]arene were found to be potential inhibitors of protein tyrosine phosphatase 1B. In the present paper, the inhibitory activity of unsubstituted sulfonyl-bridget calix[4]arene towards some of the therapeutically important protein tyrosine phosphatases has been established. The obtained results showed that the sulfonylcalix[4]arene is able to inhibit protein tyrosine phosphatase MEG2 with IC50 value in the micromolar range. At the same time, the inhibitor demonstrated lower activity in case of other protein tyrosine phosphatases such as PTP1B, MEG1, TC-PTP, SHP2, and PTPβ. The performed molecular docking indicated that the inhibitor binds to the active site region of MEG2 and PTP1B with WPD-loop in the open conformation.

Preparation and characterization of amphiphilic calixarene nanoparticles as delivery carriers for paclitaxel

Two types of amphoteric calix[n]arene carboxylic acid (CnCA) derivative, i.e., calix[6]arene hexa-carboxylic acid (C6HCA) and calix[8]arene octo-carboxylic acid (C8OCA), were synthesized by introducing acetoxyls into the hydroxyls of calix[n]arene (n=6, 8). C6HCA and C8OCA nanoparticles (NPs) were prepared successfully using the dialysis method. CnCA NPs had regular spherical shapes with an average diameter of 180-220 nm and possessed negative charges of greater than -30 mV. C6HCA and C8OCA NPs were stable in 4.5% bovine serum albumin solutions and buffers (pH 5-9), with a low critical aggregation concentration value of 5.7 mg·L(-1) and 4.0 mg·L(-1), respectively. C6HCA and C8OCA NPs exhibited good paclitaxel (PTX) loading capacity, with drug loading contents of 7.5% and 8.3%, respectively. The overall in vitro release behavior of PTX from the CnCA NPs was sustained, and C8OCA NPs had a slower release rate compared with C6HCA NPs. These favorable properties of CnCA NPs make them promising nanocarriers for tumor-targeted drug delivery.

Synthesis, biological evaluation and molecular docking of calix[4]arene-based β-diketo derivatives as HIV-1 integrase inhibitors

In this publication, we design and report the synthesis of calix[4]arene-based β-diketo derivatives as novel HIV-1 integrase (IN) inhibitors. The target compounds were obtained using Claisen condensation, and their structures were characterized by NMR and ESI-MS. Preliminary bioassays showed that calix[4]arene-based β-diketo derivatives inhibit strand transfer (ST) with IC50 values between 5.9 and 21.2 µM. Docking studies revealed the predominant binding modes that were distinct from the binding modes of raltegravir, which suggests a novel binding region in the IN active site. Moreover, these compounds are predicted not to interact with some of the key amino acids (GLN148 and ASN155) implicated in viral resistance. Therefore, this series of compounds can further be investigated for a possible chemotype to circumvent resistance to clinical HIV-1 IN inhibitors.

Molecular drug-organiser: synthesis, characterization and biological evaluation of penicillin V and/or nalidixic acid calixarene-based podands

Two well-known antibiotic heterocycles, the 'quinolone' nalidixic acid and the β-lactam penicillin V, active at different levels of the bacterial growth process, have been attached via an ether-ester junction to the p-tert-butylcalix[4]arene lower rim, in alternate position. The resulting hydrophobic molecular drug-organisers were fully characterized, and evaluated over two Gram negative and three Gram positive reference strains, using disk diffusion assays with disks impregnated with solution of title compound in pure DMSO. An interesting activity was observed over Staphylococcus aureus ATCC 25923 with the dis-symmetrical podand incorporating one penicillin and one nalidixic ester moieties.

Biochemistry of anionic calix[n]arenes

This review treats the biological properties of the various anionic calix[n]arenes, both as soluble forms and in the colloidal state. The complexation of these molecules with amino-acids, peptides and proteins is discussed, as is their interaction with model membranes. The complexations with various Active Pharmaceutical Ingredients as complexes, for tamoxifen as solid state and colloidal structures, are treated in depth. Two sections deal with the direct biological action of the calix[n]arenes and their use as biosensors. A final section deals with the toxicity, in reality the lack of toxicity of the calix[n]arenes.

Antiseptic properties of two calix[4]arenes derivatives on the human coronavirus 229E

Facing the lack in specific antiviral treatment, it is necessary to develop new means of prevention. In the case of the Coronaviridae this family is now recognized as including potent human pathogens causing upper and lower respiratory tract infections as well as nosocomial ones. Within the purpose of developing new antiseptics molecules, the antiseptic virucidal activity of two calix[4]arene derivatives, the tetra-para-sulfonato-calix[4]arene (C[4]S) and the 1,3-bis(bithiazolyl)-tetra-para-sulfonato-calix[4]arene (C[4]S-BTZ) were evaluated toward the human coronavirus 229E (HCoV 229E). Comparing these results with some obtained previously with chlorhexidine and hexamidine, (i) these two calixarenes did not show any cytotoxicity contrary to chlorhexidine and hexamidine, (ii) C[4]S showed as did hexamidine, a very weak activity against HCoV 229E, and (iii) the C[4]S-BTZ showed a stronger activity than chlorhexidine, i.e. 2.7 and 1.4log₁₀ reduction in viral titer after 5min of contact with 10⁻³mol L⁻¹ solutions of C[4]S-BTZ and chlorhexidine, respectively. Thus, the C[4]S-BTZ appeared as a promising virucidal (antiseptic) molecule.