Synthesis and antitumor activity of new benzoheterocyclic derivatives of distamycin A

A sustainable avenue for the synthesis of propargylamines and benzofurans using a Cu-functionalized MIL-101(Cr) as a reusable heterogeneous catalyst

A heterogeneous copper-catalyzed A3 coupling reaction of aldehydes, amines, and alkynes for the synthesis of propargylamines and benzofurans has been developed. Here, the modified metal-organic framework MIL-101(Cr)-SB-Cu complex was chosen as the heterogeneous copper catalyst and prepared via post-synthetic modification of amino-functionalized MIL-101(Cr). The structure, morphology, thermal stability, and copper content of the catalyst were determined by FT-IR, PXRD, SEM, TEM, EDX, TGA, XPS, and ICP-OES. The catalyst shows high catalytic activity for the aforementioned reactions under solvent-free reaction conditions. High yields, low catalyst loading, easy catalyst recovery and reusability with not much shrink in catalytic activity, and a good yield of 82% in gram-scale synthesis are some of the benefits of this protocol that drove it towards sustainability.

Recent Advances in Multicomponent Reactions Catalysed under Operationally Heterogeneous Conditions

Multicomponent reactions (MCRs) have been gaining significance and attention over the past decade because of their ability to furnish complex products by using readily available and simple starting materials while simultaneously eliminating the need to separate and purify any intermediates. More so, most of these products have been found to exhibit diverse biological activities. Another paradigm shift which has occurred contemporarily is the switch to heterogeneous catalysis, which results in additional benefits such as the reduction of waste and an increase in the safety of the process. More importantly, it allows the user to recover and reuse the catalyst for multiple runs. In summary, both methodologies adhere to the principles of green chemistry, a philosophy which needs to become overarchingly enshrined. The plethora of reactions and catalysts which have been developed gives hope that chemists are slowly changing their ideology. As a result, this review attempts to discuss multicomponent reactions catalysed by operationally heterogeneous catalysts in the past 10 years. In this review, a further distinction is made between the MCRs which lead to the formation of heterocycles and those which do not.

Nanocrystalline ZnO: A Competent and Reusable Catalyst for the Preparation of Pharmacology Relevant Heterocycles in the Aqueous Medium

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Nanoparticle catalyzed synthesis is a green and convenient method to achieve most of the chemical transformations in water or other green solvents. Nanoparticle ensures an easy isolation process of catalyst as well as products from the reaction mixture avoiding the hectic work up procedure. Zinc oxide is a biocompatible, environmentally benign and economically viable nanocatalyst with effectivity comparable to the other metal nanocatalyst employed in several reaction strategies. This review mainly focuses on the recent applications of zinc oxide in the synthesis of biologically important heterocyclic molecules under sustainable reaction conditions.

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Application of zinc oxide in organic synthesis: Considering the achievable advantages of this nanocatalyst, presently several research groups are paying attention in anchoring zincoxide or its modified structure in several types of organic conversions e.g. multicomponent reactions, ligand-free coupling reactions, cycloaddition reaction, etc. The advantages and limitations of this nanocatalyst are also demonstrated. The present study aims to highlight the recent multifaceted applications of ZnO towards the synthesis of diverse heterocyclic motifs. Being a promising biocompatible nanoparticle, this catalyst has an important contribution in the fields of synthetic chemistry and medicinal chemistry.

Preparation andin vitrobioactivity evaluation of N-heterocyclic-linked dihomooxacalix[4]arene derivatives

Based on the superior prospects of calixarenes-based agents and N-heterocyclic pharmacophores in biomedical applications, 14 new dihomooxacalix[4]arene N-heterocyclic (pyridine, quinoline, and thiazole) derivatives 4a–4n were efficiently synthesized from the parent compound, namely, p-tert-butyldihomooxacalix[4]arene 1; they were further investigated by using their IR, ¹H NMR, ¹³C NMR, and HRMS spectra. Among these derivatives, the crystal and molecular structures of 2-aminomethyl-pyridine-substituted dihomooxacalix[4]arene 4f (obtained from methanol) have been determined by X-ray diffraction. In the case of the inhibition assay of cell growth, we evaluated the effects on four select tumor cell lines (MCF-7, HepG2, SKOV3, and HeLa), as well as the normal cell lines of HUVEC, using paclitaxel as the positive control drug. It was found that the derivatives 4d–4f, 4i, 4k, and 4l could inhibit tumoral activity up to varying degrees. Mechanistically, the cell cycle analysis demonstrated that dihomooxacalix[4]arene N-heterocyclic derivatives could induce apoptosis of MCF cells. In addition, the results of the western blot and immunofluorescence studies revealed the upregulation of the protein expression levels of Bax and cleaved caspase-3, as well as the downregulation of Bcl-2, which are in good agreement with the corresponding inhibitory potencies. Therefore, these findings suggest that N-heterocyclic derivatives based on the dihomooxacalix[4]arene scaffold are promising candidates for use against cancer.

Based on superior prospects of calixarenes in biomedical fields, the bioactivity of novel N-heterocyclic linked dihomooxacalix[4]arene derivatives 4a–4n were evaluated in vitro. The crystal structure of 4f was also determined by X-ray diffraction.

An overview of recent advances in duplex DNA recognition by small molecules

As the carrier of genetic information, the DNA double helix interacts with many natural ligands during the cell cycle, and is amenable to such intervention in diseases such as cancer biogenesis. Proteins bind DNA in a site-specific manner, not only distinguishing between the geometry of the major and minor grooves, but also by making close contacts with individual bases within the local helix architecture. Over the last four decades, much research has been reported on the development of small non-natural ligands as therapeutics to either block, or in some cases, mimic a DNA–protein interaction of interest. This review presents the latest findings in the pursuit of novel synthetic DNA binders. This article provides recent coverage of major strategies (such as groove recognition, intercalation and cross-linking) adopted in the duplex DNA recognition by small molecules, with an emphasis on major works of the past few years.

Exploration of Novel Inhibitors for Class I Histone Deacetylase Isoforms by QSAR Modeling and Molecular Dynamics Simulation Assays

Histone deacetylases (HDAC) are metal-dependent enzymes and considered as important targets for cell functioning. Particularly, higher expression of class I HDACs is common in the onset of multiple malignancies which results in deregulation of many target genes involved in cell growth, differentiation and survival. Although substantial attempts have been made to control the irregular functioning of HDACs by employing various inhibitors with high sensitivity towards transformed cells, limited success has been achieved in epigenetic cancer therapy. Here in this study, we used ligand-based pharmacophore and 2-dimensional quantitative structure activity relationship (QSAR) modeling approaches for targeting class I HDAC isoforms. Pharmacophore models were generated by taking into account the known IC50 values and experimental energy scores with extensive validations. The QSAR model having an external R2 value of 0.93 was employed for virtual screening of compound libraries. 10 potential lead compounds (C1-C10) were short-listed having strong binding affinities for HDACs, out of which 2 compounds (C8 and C9) were able to interact with all members of class I HDACs. The potential binding modes of HDAC2 and HDAC8 to C8 were explored through molecular dynamics simulations. Overall, bioactivity and ligand efficiency (binding energy/non-hydrogen atoms) profiles suggested that proposed hits may be more effective inhibitors for cancer therapy.

Synthesis of New Benzofuran-2-Carboxylic Acid Derivatives

Novel ethyl ester and methylamide of 5-[bis(2-chloroethyl)amino]-7-methoxybenzofuran-2-carboxylic acid as well as (2-hydroxy-1,1-dimethylethyl)amides of 5-bromo- and 5,7-dichlorobenzofuran-2-carboxylic acid were synthesized and characterized.

Effects of biomaterials for Lab-on-a-chip production on cell growth and expression of differentiated functions of leukemic cell lines

The rapid increase of the applications for Lab-on-a-chip devices has attracted the interest of researchers and engineers on standard process of the electronics industry for low production costs and large scale development, necessary for disposable applications. The printed circuit board technology could be used for this purpose, in particular for the wide range of materials available. In this paper, assays on biocompatibility of materials used for Lab-on-a-chip fabrication has been carried out using two tumor cell lines growing in suspension, the human chronic myelogenous leukemia K562 cell line, able to undergo erythroid differentiation when cultured with chemical inducers, and the lymphoblastoid cell line (LCL), extensively used for screening of cytotoxic T-lymphocytes (CTLs). We have demonstrated that some materials strongly inhibit cell proliferation of both the two cell lines to an extent higher that 70-75%, but only after a prolonged exposure of 3-6 days (Copper, Gold over Nickel, Aramid fiber filled epoxy uncured, b-stage epoxy die attach film, Tesa 4985 adhesive tape, Pyralux uncured, Copper + 1-octodecanethiol). However, when experiments were performed with short incubation time (1 h), only Aramid fiber filled epoxy uncured was cytotoxic. Variation of the results concerning the other materials was appreciable when the experiments performed on two cell lines were compared together. Furthermore, the effects of the materials on erythroid differentiation and CTL-mediated LCL lysis confirmed, in most of the cases, the data obtained in cytotoxic and antiproliferative tests.

Liposomes- and ethosomes-associated distamycins: a comparative study

The present article describes a comparative study of the performances of liposomes and ethosomes as specialized delivery systems for distamycin A (DA) and two of its derivatives. Liposomes and ethosomes were prepared by classical methods, extruded through polycarbonate filters, and characterized in terms of dimensions, morphology, and encapsulation efficiency. It was found that DA was associated with vesicles (either liposomes or ethosomes) by around 16.0%, while both derivatives of DA showed a percentage of association around 80% in the case of liposomes and around 50% in the case of ethosomes. In vitro antiproliferative activity experiments performed on cultured human and mouse leukemic cells demonstrated that vesicles were able to increase the activity of both derivatives of DA. In addition, it was demonstrated that the aging of both liposomes- and ethosomes-associated distamycin suspensions did not heavily influence the vesicle size, while all samples showed a relevant drug leakage with time. Moreover, according to the different physicochemical characteristics of DA and its derivatives (i.e., log P), vesicle-associated DA showed the highest loss of drug with respect to both its derivatives. In conclusion, the enhancement of drug activity expressed by these specialized delivery systems-associated DD could be interesting to obtain an efficient therapeutic effect aimed at reducing or minimizing toxic effects occurring with distamycins administration.

The usefulness of cyclic diamidines with different core-substituents as antitumor agents

A series of related polycationic compounds has been screened for potential antitumor activity by the NCI's in vitro testing (one dose primary anticancer assay and the NCI-60 full panel screening). The GI50 values of triazines 3 and 4 are on average 1.9 microM and 2.4 microM, respectively. Furan 8 deserves mention too (1.9 microM). The biological test results showed that carbazole 10 possessed cytotoxic activity in the nanomolar range, much better than the other compounds tested, only against several cancer cell lines: CCRF-CEM, HL-60(TB), MOLT-4, NCI-H522, COLO 205, SF-268, but the average GI50 value was higher (15 microM). The activity appears closely dependent on the core-shape and length of the bisimidazoline molecules (important for both high cytotoxicity and DNA binding). The mechanism of DNA minor-groove binding of diamidines 1-12, based on the anticancer parameters, is highly probable.

Evaluation of radiolabeled (hetero)aromatic analogues of N-(2-diethylaminoethyl)-4-iodobenzamide for imaging and targeted radionuclide therapy of melanoma

Targeted radionuclide therapy using radioiodinated compounds with a specific affinity for melanoma tissue is a promising treatment for disseminated melanoma, but the candidate with the ideal kinetic profile remains to be discovered. Targeted radionuclide therapy concentrates the effects on tumor cells, thereby increasing the efficacy and decreasing the morbidity of radiotherapy. In this context, analogues of N-(2-diethylaminoethyl)-4-iodobenzamide (BZA) are of interest. Various (hetero)aromatic analogues 5 of BZA were synthesized and radioiodinated with (125)I, and their biodistribution in melanoma-bearing mice was studied after i.v. administration. Most [ (125)I] 5-labeled compounds appeared to bind specifically and with moderate-to-high affinity to melanoma tumor. Two compounds, 5h and 5k, stood out with high specific and long-lasting uptake in the tumor, with a 7- and 16-fold higher value than BZA at 72 h, respectively, and kinetic profiles that makes them promising agents for internal targeted radionuclide therapy of melanoma.

Hybrid molecules containing benzo[4,5]imidazo[1,2-d][1,2,4]thiadiazole and α-bromoacryloyl moieties as potent apoptosis inducers on human myeloid leukaemia cells

The synthesis and biological activity of a series of hybrids 1-5 prepared combining a benzo[4,5]imidazo[1,2-d][1,2,4]thiadiazole and different benzoheterocyclic alpha-bromoacryloyl amides have been described and their structure-activity relationships discussed. All these hetero-bifunctional compounds were highly cytotoxic against the human myeloid leukaemia cell lines HL-60 and U937 (IC(50) 0.24-1.72microM), significantly superior to that of both alkylating units alone. In human myeloid leukaemia HL-60 cells we observed that these compounds suppress survival and proliferation by triggering morphological changes and internucleosomal DNA fragmentation characteristic of apoptotic cell death. The apoptosis induced by these compounds is mediated by caspase-3 activation and is also associated to an early release of cytochrome c from the mitochondria.

Liposomes and micellar dispersions for delivery of benzoheterocyclic derivatives of distamycin A

In this article we describe the production and characterization of specialized delivery systems for some distamycin derivatives (DD), namely liposomes and micellar dispersions. All the formulations were designed to increase the solubility of DD in an aqueous environment and to reduce the possible toxicity problems related to the administration of these drugs. For instance, liposomes were prepared by reverse phase evaporation technique followed by extrusion through polycarbonate filters, then characterized in terms of dimensions, morphology, and encapsulation efficacy. The analysis of their in vitro antiproliferative activity on cultured human and mouse leukemic cells demonstrated that liposomes and micellar dispersions containing DD exert quite different effects. These effects were compared with those shown by the free drug depending on type of drug and also cell line used.

Synthesis and biological activity of alpha-bromoacryloyl lexitropsin conjugates

The design, synthesis and biological evaluation of lexitropsins bearing mixed heterocyclic and benzoheterocyclic moieties and tethered to an alpha-bromo acrylic moiety acting as alkylating moiety are reported, and structure-activity relationships determined. With respect to antiproliferative activity against L1210 and K562 cells, compounds 7 and 10 showed the greatest potency, while compounds 4 and 5 exhibit the lowest activity. Among the synthesized compounds 4-12, the derivative 10 was found to be the most potent member of this class and it is 70-fold more active than the bis-pyrrole counterpart 3 against L1210 cell line. In addition, the cytotoxicity of derivatives 5-12 against KB cells and the influence of different glutathione (GSH) concentrations on the cytotoxic effects was also investigated.

Liposomes containing distamycins: preparation, characterization and antiproliferative activity

This article describes the production and characterization of two liposome formulations containing antitumor drugs, namely distamycin A (Dist) and a new alkyl derivative of distamycin A (C16-Dist). Egg-PC/cholesterol liposomes (4:1 mol/mol) were prepared by reverse phase evaporation technique followed by extrusion through polycarbonate filters. The encapsulation efficiency was found to be almost complete for C16-Dist (99.8%), while native distamycin A showed a lower yield (19.0%). The in vitro antiproliferative activity of the distamycins-containing liposomes determined on human leukaemic K562 cells, was 11-fold and 8-fold higher for native and alkyl derivative distamycin A, respectively, compared with that of the corresponding free drugs. Liposomal formulations show an increase in the activity and specificity of distamycins in experimental antitumor therapy.

LC-MS-MS determination of brostallicin in human plasma following automated on-line SPE

LC-MS-MS method using automated on-line solid-phase extraction (SPE) has been developed and validated for the quantitation of brostallicin (I), a new distamycin derivative, in human plasma. I is a DNA minor groove binder currently under phase I-II clinical evaluation as an anticancer drug. Plasma (0.4 ml) was spiked with 0.2 ml stable label IS solution and placed in a 96-well plate maintained at +4 degrees C. Aliquots of 0.1 ml of prepared samples were loaded into the on-line SPE HySphere Resin SH cartridges (10 mm x 2 mm ID) and the analytes back eluted with the mobile phase into LC-MS-MS system. A Platinum Cyano column (100 mm x 4.6 mm, 3.6 microm) was used to perform the chromatographic analysis. The mobile phase was acetonitrile-ammonium formate buffer (pH 3.5; 20 mM) (70:30, v/v) at a flow rate of 1.0 ml/min. LC flow was split so that 300 microl/min was directed toward the mass spectrometer interface. Retention time of I was 2.6 min and the total cycle time was 8 min. MS detection used an Applied Biosystems/MDS SCIEX API 365 with a TurboIonSpray interface and MRM (m/Z: 725/257 for I and m/Z: 729/257 for IS) operated in positive ion mode. The method was validated over the calibration range 0.124-497 ng/ml. A negligible carry-over effect from the system was observed. In spite of the known instability of I in human plasma (about 20% decrease over 12 h), the ratio analyte/IS peak area showed good stability over the analysis time required for 96 samples. The automated on-line SPE method can be considered as a valid alternative to the off-line manual SPE procedure previously developed.

Levitation and movement of human tumor cells using a printed circuit board device based on software-controlled dielectrophoresis

In this study we describe an original, efficient, and innovative printed circuit board (PCB) device able to generate dielectrophoresis-based, software-controlled cages that can be moved to any place inside a microchamber. Depending on their dielectrophoretic properties, eukaryotic cells can be "entrapped" in cages and moved under software control. The main conclusion gathered from the experimental data reported is that the PCB device based on dielectrophoresis permits levitation and movement of different tumor cells at different dielectrophoresis conditions. The results presented herein are therefore the basis for experiments aimed at forced interactions or separation of eukaryotic cells using "lab-on-a-chip." In fact, because many cages can be controlled at the same time, and two or more cages can be forced to share the same or a different location, it is possible, in principle, either to bring in contact cells of a differing histotype or to separate them.

Synthesis and growth inhibition activity of alpha-bromoacrylic heterocyclic and benzoheterocyclic derivatives of distamycin A modified on the amidino moiety

The design, synthesis and in vitro activities of novel alpha-bromoacryloyl pyrazole, imidazole and benzoheterocyclic derivatives of distamycin A, in which the amidino moiety has been replaced by moieties of different physico-chemical features are described, and the structure-activity relationships are discussed. In spite of the relevance of these modifications on the distamycin frame, these derivatives showed significant growth inhibitory activity against mouse leukemia L1210 cells. Therefore, the presence of the amidino moiety, and in general of a basic moiety, is not an absolute requirement for biological activity of alpha-bromoacrylic derivatives of distamycin.

Benzoyl and cinnamoyl nitrogen mustard derivatives of benzoheterocyclic analogues of the tallimustine: synthesis and antitumour activity

A series of benzoyl and cinnamoyl nitrogen mustards tethered to different benzoheterocycles and to oligopyrroles structurally related to netropsin consisting of two pyrrole-amide units and terminating with an amidine moiety have been synthesised and a structure--activity relationship determined. Derivatives 3--10 have been evaluated for their sequence selective alkylating properties and cytotoxicity against human K562 leukaemia cells. They are 2- to 50-fold less cytotoxic than tallimustine, with compound 8 being the most potent member of this series. Among tallimustine isosters, the compounds with an indole 3 or benzothiophene 6 are 4-fold less cytotoxic than tallimustine, while the compounds with an N-methyl indole or benzofuran showed a 7- and 14-fold reduced cytotoxic potency, respectively. Our preliminary results indicate that these derivatives preferentially bind to AT-rich sequence with a sequence selectivity similar to tallimustine.

Accumulation of gamma-globin mRNA and induction of erythroid differentiation after treatment of human leukaemic K562 cells with tallimustine

Human leukaemic K562 cells can be induced in vitro to erythroid differentiation by a variety of chemical compounds, including haemin, butyric acid, 5-azacytidine, cytosine arabinoside, mithramycin and chromomycin, cisplatin and cisplatin analogues. Differentiation of K562 cells is associated with an increase of expression of embryo-fetal globin genes, such as the zeta-, epsilon- and gamma-globin genes. The K562 cell line has been proposed as a very useful in vitro model system to determine the therapeutic potential of new differentiating compounds as well as to study the molecular mechanism(s) regulating changes in the expression of embryonic and fetal human globin genes. Inducers of erythroid differentiation stimulating gamma-globin synthesis could be considered for possible use in the therapy of haematological diseases associated with a failure in the expression of normal beta-globin genes. We have analysed the effects of tallimustine and distamycin on cell growth and differentiation of K562 cells. The results demonstrated that tallimustine is a potent inducer, while distamycin is a weak inducer, of K562 cell erythroid differentiation. Erythroid differentiation was associated with an increase of accumulation of gamma-globin mRNA and of production of both haemoglobin (Hb) Gower 1 and Hb Portland. In addition, tallimustine-mediated erythroid induction occurred in the presence of activation of the apoptotic pathway. The reasons for proposing tallimustine as an inducer of gamma-globin gene expression are strongly sustained by the finding that this compound stimulates fetal haemoglobin production in human erythroid precursor cells from normal subjects.